chore: initial git load of code space

tests/Strata.SqlTools.PostgreSql.Tests/PostgreSql/CTEColumnListTests.cs

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+using Strata.SqlTools.Breakdowns.PostgreSql;
+using Strata.SqlTools.SqlBreakdown.Classes;
+
+namespace Strata.SqlTools.PostgreSql.Tests;
+
+[TestFixture]
+public class CTEColumnListTests
+{
+    #region Basic Column List Tests
+
+    [Test]
+    public void WithClause_ColumnList_CanBeSet()
+    {
+        // Arrange
+        var cte = new QueryBreakdown("id, name, email", "users");
+        var withClause = new WithClause("user_summary", cte)
+        {
+            ColumnList = new List<string> { "user_id", "user_name", "user_email" }
+        };
+
+        // Act & Assert
+        Assert.That(withClause.ColumnList, Has.Count.EqualTo(3));
+        Assert.That(withClause.ColumnList[0], Is.EqualTo("user_id"));
+        Assert.That(withClause.ColumnList[1], Is.EqualTo("user_name"));
+        Assert.That(withClause.ColumnList[2], Is.EqualTo("user_email"));
+    }
+
+    [Test]
+    public void GetSql_WithColumnList_IncludesColumnsInWithClauseName()
+    {
+        // Arrange
+        var cte = new QueryBreakdown("id, name, email", "users", "active = true");
+        var mainQuery = new QueryBreakdown("*", "active_users");
+
+        var withClause = new WithClause("active_users", cte)
+        {
+            ColumnList = new List<string> { "user_id", "user_name", "user_email" }
+        };
+        mainQuery.AddWithClause(withClause);
+
+        // Act
+        var sql = mainQuery.GetSql();
+
+        // Assert
+        Assert.That(sql, Contains.Substring("active_users (user_id, user_name, user_email)"),
+            "SQL should include column list in CTE definition");
+    }
+
+    [Test]
+    public void GetSql_WithoutColumnList_DoesNotIncludeParens()
+    {
+        // Arrange
+        var cte = new QueryBreakdown("id, name, email", "users");
+        var mainQuery = new QueryBreakdown("*", "all_users");
+
+        var withClause = new WithClause("all_users", cte)
+        {
+            ColumnList = null
+        };
+        mainQuery.AddWithClause(withClause);
+
+        // Act
+        var sql = mainQuery.GetSql();
+
+        // Assert
+        Assert.That(sql, Contains.Substring("all_users AS"));
+        Assert.That(sql, Does.Not.Contain("all_users ()"));
+    }
+
+    [Test]
+    public void GetSql_WithEmptyColumnList_DoesNotIncludeParens()
+    {
+        // Arrange
+        var cte = new QueryBreakdown("id, name", "users");
+        var mainQuery = new QueryBreakdown("*", "data");
+
+        var withClause = new WithClause("data", cte)
+        {
+            ColumnList = new List<string>()
+        };
+        mainQuery.AddWithClause(withClause);
+
+        // Act
+        var sql = mainQuery.GetSql();
+
+        // Assert
+        Assert.That(sql, Contains.Substring("data AS"));
+        Assert.That(sql, Does.Not.Contain("data ()"));
+    }
+
+    #endregion
+
+    #region Multi-CTE Column List Tests
+
+    [Test]
+    public void GetSql_WithMultipleCTEsWithColumnLists_IncludesAllLists()
+    {
+        // Arrange
+        var cte1 = new QueryBreakdown("id, name", "users");
+        var cte2 = new QueryBreakdown("user_id, order_count", "orders");
+
+        var mainQuery = new QueryBreakdown("*", "results");
+
+        var withClause1 = new WithClause("active_users", cte1)
+        {
+            ColumnList = new List<string> { "user_id", "user_name" }
+        };
+
+        var withClause2 = new WithClause("user_orders", cte2)
+        {
+            ColumnList = new List<string> { "uid", "order_count" }
+        };
+
+        mainQuery.AddWithClause(withClause1);
+        mainQuery.AddWithClause(withClause2);
+
+        // Act
+        var sql = mainQuery.GetSql();
+
+        // Assert
+        Assert.That(sql, Contains.Substring("active_users (user_id, user_name)"));
+        Assert.That(sql, Contains.Substring("user_orders (uid, order_count)"));
+    }
+
+    #endregion
+
+    #region Column List with Parameters (PostgreSQL-style positional parameters)
+
+    [Test]
+    public void ColumnList_PreservesPostgresqlParameters()
+    {
+        // Arrange
+        var cte = new QueryBreakdown("id, name, salary", "employees", "salary > $1");
+        cte.AddParameter("MinSalary", 50000);
+
+        var mainQuery = new QueryBreakdown("*", "high_earners");
+
+        var withClause = new WithClause("high_earners", cte)
+        {
+            ColumnList = new List<string> { "emp_id", "emp_name", "emp_salary" }
+        };
+        mainQuery.AddWithClause(withClause);
+
+        // Act
+        var sql = mainQuery.GetSql();
+        var merged = mainQuery.GetMergedParameters();
+
+        // Assert
+        Assert.That(sql, Contains.Substring("high_earners (emp_id, emp_name, emp_salary)"));
+        var keys = merged.Keys.ToList();
+        Assert.That(keys.Any(k => k.Contains("MinSalary")), "Parameters should be preserved with column list");
+    }
+
+    #endregion
+
+    #region Column List with Recursive CTEs
+
+    [Test]
+    public void ColumnList_WorksWithRecursiveCTE()
+    {
+        // Arrange
+        var anchorQuery = new QueryBreakdown("id, manager_id, name, 1 as level", "employees", "manager_id IS NULL");
+        var recursiveQuery = new QueryBreakdown(
+            "e.id, e.manager_id, e.name, h.level + 1",
+            "employees e INNER JOIN hierarchy h ON e.manager_id = h.id"
+        );
+
+        var mainQuery = new QueryBreakdown("*", "hierarchy");
+
+        var withClause = new WithClause("hierarchy", anchorQuery)
+        {
+            IsRecursive = true,
+            RecursiveQuery = recursiveQuery,
+            ColumnList = new List<string> { "emp_id", "mgr_id", "emp_name", "lvl" }
+        };
+        mainQuery.AddWithClause(withClause);
+
+        // Act
+        var sql = mainQuery.GetSql();
+
+        // Assert
+        Assert.That(sql, Contains.Substring("WITH RECURSIVE"));
+        Assert.That(sql, Contains.Substring("hierarchy (emp_id, mgr_id, emp_name, lvl)"));
+        Assert.That(sql, Contains.Substring("UNION ALL"));
+    }
+
+    #endregion
+
+    #region Column List Length and Naming
+
+    [Test]
+    public void ColumnList_PreservesColumnOrder()
+    {
+        // Arrange
+        var cte = new QueryBreakdown("a, b, c", "source");
+        var mainQuery = new QueryBreakdown("*", "output");
+
+        var columns = new List<string> { "z", "y", "x" };
+        var withClause = new WithClause("ordered_cte", cte)
+        {
+            ColumnList = columns
+        };
+        mainQuery.AddWithClause(withClause);
+
+        // Act
+        var sql = mainQuery.GetSql();
+
+        // Assert
+        Assert.That(sql, Contains.Substring("ordered_cte (z, y, x)"));
+    }
+
+    [Test]
+    public void ColumnList_AllowsQuotedIdentifiers()
+    {
+        // Arrange
+        var cte = new QueryBreakdown("col1, col2", "source");
+        var mainQuery = new QueryBreakdown("*", "output");
+
+        var columns = new List<string> { "\"Column 1\"", "\"column-2\"" };
+        var withClause = new WithClause("quoted_cte", cte)
+        {
+            ColumnList = columns
+        };
+        mainQuery.AddWithClause(withClause);
+
+        // Act
+        var sql = mainQuery.GetSql();
+
+        // Assert
+        Assert.That(sql, Contains.Substring("quoted_cte (\"Column 1\", \"column-2\")"));
+    }
+
+    #endregion
+
+    #region Real-World Scenarios
+
+    [Test]
+    public void ColumnList_PostgresqlAnalyticsScenario()
+    {
+        // Scenario: PostgreSQL analytics with window functions and renamed columns
+        // Arrange
+        var analyticsData = new QueryBreakdown(
+            "transaction_date, product_id, customer_id, amount, ROW_NUMBER() OVER (PARTITION BY customer_id ORDER BY transaction_date) as rank",
+            "transactions",
+            "transaction_date >= $1 AND amount >= $2"
+        );
+        analyticsData.AddParameter("StartDate", DateTime.Today.AddMonths(-6));
+        analyticsData.AddParameter("MinAmount", 100);
+
+        var mainQuery = new QueryBreakdown("*", "ranked_transactions");
+
+        var withClause = new WithClause("customer_transactions", analyticsData)
+        {
+            ColumnList = new List<string>
+            {
+                "trans_date",
+                "prod_id",
+                "cust_id",
+                "trans_amount",
+                "transaction_rank"
+            }
+        };
+        mainQuery.AddWithClause(withClause);
+
+        // Act
+        var sql = mainQuery.GetSql();
+        var params_all = mainQuery.GetMergedParameters();
+
+        // Assert
+        Assert.That(sql, Contains.Substring("customer_transactions (trans_date, prod_id, cust_id, trans_amount, transaction_rank)"));
+        var paramKeys = params_all.Keys.ToList();
+        Assert.That(paramKeys.Any(k => k.Contains("StartDate")));
+        Assert.That(paramKeys.Any(k => k.Contains("MinAmount")));
+    }
+
+    #endregion
+}

tests/Strata.SqlTools.PostgreSql.Tests/PostgreSql/QueryBreakdownCollectionTests.cs

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+using Strata.SqlTools.Breakdowns.PostgreSql;
+
+namespace Strata.SqlTools.SqlBreakdown.Tests.PostgreSql;
+
+[TestFixture]
+public class QueryBreakdownCollectionTests
+{
+    private QueryBreakdownCollection _collection = null!;
+
+    [SetUp]
+    public void Setup()
+    {
+        _collection = new QueryBreakdownCollection();
+    }
+
+    #region Constructor Tests
+
+    [Test]
+    public void Constructor_Default_CreatesEmptyCollection()
+    {
+        // Arrange & Act
+        var collection = new QueryBreakdownCollection();
+
+        // Assert
+        Assert.That(collection.Count, Is.EqualTo(0));
+    }
+
+    #endregion
+
+    #region Add Tests
+
+    [Test]
+    public void Add_SingleQueryBreakdown_AddsSuccessfully()
+    {
+        // Arrange
+        var query = new QueryBreakdown("id, name", "users");
+
+        // Act
+        _collection.Add(query);
+
+        // Assert
+        Assert.That(_collection.Count, Is.GreaterThan(0));
+    }
+
+    [Test]
+    public void Add_MultipleQueryBreakdowns_AddsMultiple()
+    {
+        // Arrange
+        var query1 = new QueryBreakdown("id, name", "users");
+        var query2 = new QueryBreakdown("order_id, amount", "orders");
+        var query3 = new QueryBreakdown("product_id, price", "products");
+
+        // Act
+        _collection.Add(query1);
+        _collection.Add(query2);
+        _collection.Add(query3);
+
+        // Assert
+        Assert.That(_collection.Count, Is.EqualTo(3));
+    }
+
+    #endregion
+
+    #region GetPostgreSqlBatch Tests
+
+    [Test]
+    public void GetPostgreSqlBatch_EmptyCollection_ReturnsEmptyString()
+    {
+        // Arrange - empty collection created in SetUp
+
+        // Act
+        var sql = _collection.GetPostgreSqlBatch();
+
+        // Assert
+        Assert.That(sql, Is.Not.Null);
+    }
+
+    [Test]
+    public void GetPostgreSqlBatch_SingleQuery_GeneratesValidSql()
+    {
+        // Arrange
+        var query = new QueryBreakdown("id, name", "users");
+        _collection.Add(query);
+
+        // Act
+        var sql = _collection.GetPostgreSqlBatch();
+
+        // Assert
+        Assert.That(sql, Is.Not.Null);
+        Assert.That(sql, Does.Contain("SELECT").Or.Contain("select"));
+    }
+
+    [Test]
+    public void GetPostgreSqlBatch_MultipleQueries_SeparatesWithSemicolon()
+    {
+        // Arrange
+        var query1 = new QueryBreakdown("id", "users");
+        var query2 = new QueryBreakdown("id", "orders");
+        _collection.Add(query1);
+        _collection.Add(query2);
+
+        // Act
+        var sql = _collection.GetPostgreSqlBatch();
+
+        // Assert
+        Assert.That(sql, Is.Not.Null);
+        // PostgreSQL batch should contain semicolons separating statements
+        Assert.That(sql, Does.Contain(";"));
+    }
+
+    [Test]
+    public void GetPostgreSqlBatch_WithWhereClause_IncludesConditions()
+    {
+        // Arrange
+        var query = new QueryBreakdown("id, name", "users");
+        query.WhereClause.Clause = "active = true";
+        _collection.Add(query);
+
+        // Act
+        var sql = _collection.GetPostgreSqlBatch();
+
+        // Assert
+        Assert.That(sql, Does.Contain("active"));
+    }
+
+    [Test]
+    public void GetPostgreSqlBatch_WithOrderBy_IncludesOrderBy()
+    {
+        // Arrange
+        var query = new QueryBreakdown("id, name", "users");
+        query.OrderByClause.Clause = "name ASC";
+        _collection.Add(query);
+
+        // Act
+        var sql = _collection.GetPostgreSqlBatch();
+
+        // Assert
+        Assert.That(sql, Does.Contain("ORDER BY").Or.Contain("order by"));
+    }
+
+    [Test]
+    public void GetPostgreSqlBatch_WithGroupBy_IncludesGroupBy()
+    {
+        // Arrange
+        var query = new QueryBreakdown("category, COUNT(*) as count", "products");
+        query.GroupByClause.Clause = "category";
+        _collection.Add(query);
+
+        // Act
+        var sql = _collection.GetPostgreSqlBatch();
+
+        // Assert
+        Assert.That(sql, Does.Contain("GROUP BY").Or.Contain("group by"));
+    }
+
+    [Test]
+    public void GetPostgreSqlBatch_WithHaving_IncludesHaving()
+    {
+        // Arrange
+        var query = new QueryBreakdown("category, COUNT(*) as count", "products");
+        query.GroupByClause.Clause = "category";
+        query.HavingClause.Clause = "COUNT(*) > 5";
+        _collection.Add(query);
+
+        // Act
+        var sql = _collection.GetPostgreSqlBatch();
+
+        // Assert
+        Assert.That(sql, Does.Contain("HAVING").Or.Contain("having"));
+    }
+
+    #endregion
+
+    #region ParseBatch Tests
+
+    [Test]
+    public void ParseBatch_WithValidSql_Succeeds()
+    {
+        // Arrange
+        var batchSql = "SELECT id, name FROM users WHERE active = true; SELECT order_id FROM orders;";
+
+        // Act
+        var result = _collection.ParseBatch(batchSql);
+
+        // Assert
+        Assert.That(result, Is.True);
+        Assert.That(_collection.Count, Is.GreaterThan(0));
+    }
+
+    [Test]
+    public void ParseBatch_WithMultipleStatements_ParsesAllQueries()
+    {
+        // Arrange
+        var batchSql = @"
+            SELECT id, name FROM users WHERE active = true;
+            SELECT order_id, amount FROM orders WHERE user_id = $1;
+        ";
+
+        // Act
+        var result = _collection.ParseBatch(batchSql);
+
+        // Assert
+        Assert.That(result, Is.True);
+        Assert.That(_collection.Count, Is.GreaterThan(0));
+    }
+
+    [Test]
+    public void ParseBatch_WithSingleStatement_ParsesSingleQuery()
+    {
+        // Arrange
+        var batchSql = "SELECT id, name FROM users";
+
+        // Act
+        var result = _collection.ParseBatch(batchSql);
+
+        // Assert
+        Assert.That(result, Is.True);
+    }
+
+    #endregion
+
+    #region Complex Query Tests
+
+    [Test]
+    public void GetPostgreSqlBatch_ComplexQueryWithMultipleClauses_GeneratesValidBatch()
+    {
+        // Arrange
+        var query1 = new QueryBreakdown("id, name", "users");
+        query1.WhereClause.Clause = "id = $1";
+
+        var query2 = new QueryBreakdown("order_id, amount", "orders");
+        query2.WhereClause.Clause = "user_id = $1";
+        query2.OrderByClause.Clause = "created_at DESC";
+
+        _collection.Add(query1);
+        _collection.Add(query2);
+
+        // Act
+        var sql = _collection.GetPostgreSqlBatch();
+
+        // Assert
+        Assert.That(sql, Does.Contain(";"));
+        Assert.That(sql, Does.Contain("SELECT"));
+        Assert.That(sql, Does.Contain("WHERE"));
+    }
+
+    [Test]
+    public void GetPostgreSqlBatch_WithParameters_IncludesParameterValues()
+    {
+        // Arrange
+        var query = new QueryBreakdown("id, name", "users");
+        query.AddParameter("userId", 123);
+        _collection.Add(query);
+
+        // Act
+        var sql = _collection.GetPostgreSqlBatch();
+
+        // Assert
+        Assert.That(sql, Does.Contain("SELECT"));
+        Assert.That(sql, Is.Not.Null);
+    }
+
+    [Test]
+    public void GetPostgreSqlBatch_MultipleQueriesWithDifferentClauses_GeneratesValidBatch()
+    {
+        // Arrange
+        var query1 = new QueryBreakdown("id, name", "users");
+        query1.WhereClause.Clause = "active = true";
+
+        var query2 = new QueryBreakdown("order_id, total", "orders");
+        query2.WhereClause.Clause = "status = 'pending'";
+        query2.OrderByClause.Clause = "created_at DESC";
+
+        var query3 = new QueryBreakdown("product_id, price", "products");
+        query3.WhereClause.Clause = "in_stock = true";
+        query3.OrderByClause.Clause = "price ASC";
+
+        _collection.Add(query1);
+        _collection.Add(query2);
+        _collection.Add(query3);
+
+        // Act
+        var sql = _collection.GetPostgreSqlBatch();
+
+        // Assert
+        Assert.That(sql, Does.Contain("SELECT"));
+        Assert.That(sql, Does.Contain(";"));
+        Assert.That(_collection.Count, Is.EqualTo(3));
+    }
+
+    #endregion
+
+    #region Edge Cases
+
+    [Test]
+    public void GetPostgreSqlBatch_MultipleQueriesWithJoins_GeneratesValidBatch()
+    {
+        // Arrange
+        var query = new QueryBreakdown("u.id, u.name, o.order_id", "users u LEFT JOIN orders o ON u.id = o.user_id");
+        query.WhereClause.Clause = "u.active = true";
+        _collection.Add(query);
+
+        // Act
+        var sql = _collection.GetPostgreSqlBatch();
+
+        // Assert
+        Assert.That(sql, Does.Contain("JOIN"));
+    }
+
+    [Test]
+    public void GetPostgreSqlBatch_WithDoubleQuotedIdentifiers_PreservesQuotes()
+    {
+        // Arrange
+        var query = new QueryBreakdown("\"Id\", \"Name\"", "\"Users\"");
+        _collection.Add(query);
+
+        // Act
+        var sql = _collection.GetPostgreSqlBatch();
+
+        // Assert
+        Assert.That(sql, Does.Contain("\""));
+    }
+
+    [Test]
+    public void ParseBatch_WithComments_IgnoresComments()
+    {
+        // Arrange
+        var batchSql = @"
+            -- This is a user query
+            SELECT id, name FROM users;
+            -- This is an orders query
+            SELECT order_id FROM orders;
+        ";
+
+        // Act
+        var result = _collection.ParseBatch(batchSql);
+
+        // Assert
+        Assert.That(result, Is.True);
+    }
+
+    #endregion
+}

tests/Strata.SqlTools.PostgreSql.Tests/PostgreSql/QueryBreakdownTests.cs

@@ -0,0 +1,577 @@
+using Strata.SqlTools.Breakdowns.PostgreSql;
+
+namespace Strata.SqlTools.SqlBreakdown.Tests.PostgreSql;
+
+[TestFixture]
+public class QueryBreakdownTests
+{
+    #region Constructor Tests
+
+    [Test]
+    public void Constructor_Default_InitializesEmptyProperties()
+    {
+        // Arrange & Act
+        var queryBreakdown = new QueryBreakdown();
+
+        // Assert
+        Assert.That(queryBreakdown.SelectClause.Clause, Is.EqualTo(string.Empty));
+        Assert.That(queryBreakdown.FromClause.Clause, Is.EqualTo(string.Empty));
+        Assert.That(queryBreakdown.WhereClause.Clause, Is.EqualTo(string.Empty));
+        Assert.That(queryBreakdown.OrderByClause.Clause, Is.EqualTo(string.Empty));
+    }
+
+    [Test]
+    public void Constructor_WithSelectAndFrom_SetsProperties()
+    {
+        // Arrange
+        var selectClause = "id, name";
+        var fromClause = "users";
+
+        // Act
+        var queryBreakdown = new QueryBreakdown(selectClause, fromClause);
+
+        // Assert
+        Assert.That(queryBreakdown.SelectClause.Clause, Is.EqualTo(selectClause));
+        Assert.That(queryBreakdown.FromClause.Clause, Is.EqualTo(fromClause));
+    }
+
+    [Test]
+    public void Constructor_WithSelectFromAndWhere_SetsProperties()
+    {
+        // Arrange
+        var selectClause = "id, name";
+        var fromClause = "users";
+        var whereClause = "active = true";
+
+        // Act
+        var queryBreakdown = new QueryBreakdown(selectClause, fromClause, whereClause);
+
+        // Assert
+        Assert.That(queryBreakdown.SelectClause.Clause, Is.EqualTo(selectClause));
+        Assert.That(queryBreakdown.FromClause.Clause, Is.EqualTo(fromClause));
+        Assert.That(queryBreakdown.WhereClause.Clause, Is.EqualTo(whereClause));
+    }
+
+    [Test]
+    public void Constructor_WithAllBasicClauses_SetsProperties()
+    {
+        // Arrange
+        var selectClause = "id, name";
+        var fromClause = "users";
+        var whereClause = "active = true";
+        var orderByClause = "id ASC";
+
+        // Act
+        var queryBreakdown = new QueryBreakdown(selectClause, fromClause, whereClause, orderByClause);
+
+        // Assert
+        Assert.That(queryBreakdown.SelectClause.Clause, Is.EqualTo(selectClause));
+        Assert.That(queryBreakdown.FromClause.Clause, Is.EqualTo(fromClause));
+        Assert.That(queryBreakdown.WhereClause.Clause, Is.EqualTo(whereClause));
+        Assert.That(queryBreakdown.OrderByClause.Clause, Is.EqualTo(orderByClause));
+    }
+
+    #endregion
+
+    #region GetSql Tests
+
+    [Test]
+    public void GetSql_WithBasicQuery_GeneratesValidSql()
+    {
+        // Arrange
+        var queryBreakdown = new QueryBreakdown("id, name", "users");
+
+        // Act
+        var sql = queryBreakdown.GetSql();
+
+        // Assert
+        Assert.That(sql, Is.Not.Null);
+        Assert.That(sql, Does.Contain("SELECT").Or.Contain("select"));
+        Assert.That(sql, Does.Contain("users"));
+    }
+
+    [Test]
+    public void GetSql_WithWhereClause_GeneratesValidSql()
+    {
+        // Arrange
+        var queryBreakdown = new QueryBreakdown("id, name", "users", "active = true");
+
+        // Act
+        var sql = queryBreakdown.GetSql();
+
+        // Assert
+        Assert.That(sql, Does.Contain("active"));
+        Assert.That(sql, Does.Contain("true"));
+    }
+
+    [Test]
+    public void GetSql_WithOrderByClause_GeneratesValidSql()
+    {
+        // Arrange
+        var queryBreakdown = new QueryBreakdown("id, name", "users", "active = true", "name ASC");
+
+        // Act
+        var sql = queryBreakdown.GetSql();
+
+        // Assert
+        Assert.That(sql, Does.Contain("ORDER BY").Or.Contain("order by"));
+    }
+
+    #endregion
+
+    #region Parameters Tests
+
+    [Test]
+    public void AddParameter_SingleParameter_StoresParameter()
+    {
+        // Arrange
+        var queryBreakdown = new QueryBreakdown("id, name", "users");
+
+        // Act
+        queryBreakdown.AddParameter("userId", 123);
+
+        // Assert
+        Assert.That(queryBreakdown.Parameters.ContainsKey("userId"), Is.True);
+        Assert.That(queryBreakdown.Parameters["userId"], Is.EqualTo(123));
+    }
+
+    [Test]
+    public void AddParameter_MultipleParameters_StoresAll()
+    {
+        // Arrange
+        var queryBreakdown = new QueryBreakdown("id, name", "users");
+
+        // Act
+        queryBreakdown.AddParameter("param1", "value1");
+        queryBreakdown.AddParameter("param2", 123);
+        queryBreakdown.AddParameter("param3", new DateTime(2025, 1, 1));
+
+        // Assert
+        Assert.That(queryBreakdown.Parameters.Count, Is.GreaterThanOrEqualTo(3));
+        Assert.That(queryBreakdown.Parameters.ContainsKey("param1"), Is.True);
+        Assert.That(queryBreakdown.Parameters.ContainsKey("param2"), Is.True);
+        Assert.That(queryBreakdown.Parameters.ContainsKey("param3"), Is.True);
+    }
+
+    [Test]
+    public void AddParameter_ParameterWithAtPrefix_NormalizesName()
+    {
+        // Arrange
+        var queryBreakdown = new QueryBreakdown("id", "users");
+
+        // Act
+        queryBreakdown.AddParameter("@userId", 999);
+
+        // Assert
+        // The @ prefix is stripped
+        Assert.That(queryBreakdown.Parameters.Count, Is.GreaterThan(0));
+    }
+
+    #endregion
+
+    #region Parse Tests
+
+    [Test]
+    public void Parse_WithValidSelectStement_Succeeds()
+    {
+        // Arrange
+        var sql = "SELECT id, name FROM users";
+
+        // Act
+        var queryBreakdown = QueryBreakdown.Parse(sql);
+
+        // Assert
+        Assert.That(queryBreakdown, Is.Not.Null);
+        Assert.That(queryBreakdown.SelectClause.Clause, Is.Not.Empty);
+        Assert.That(queryBreakdown.FromClause.Clause, Is.Not.Empty);
+    }
+
+    [Test]
+    public void Parse_WithWhereClause_ExtractsCorrectly()
+    {
+        // Arrange
+        var sql = "SELECT id, name FROM users WHERE active = true";
+
+        // Act
+        var queryBreakdown = QueryBreakdown.Parse(sql);
+
+        // Assert
+        Assert.That(queryBreakdown.WhereClause.Clause, Is.Not.Empty);
+        Assert.That(queryBreakdown.FromClause.Clause, Does.Contain("users"));
+    }
+
+    [Test]
+    public void Parse_WithOrderBy_ExtractsCorrectly()
+    {
+        // Arrange
+        var sql = "SELECT id, name FROM users ORDER BY name ASC";
+
+        // Act
+        var queryBreakdown = QueryBreakdown.Parse(sql);
+
+        // Assert
+        Assert.That(queryBreakdown.OrderByClause.Clause, Is.Not.Empty);
+        Assert.That(queryBreakdown.OrderByClause.Clause, Does.Contain("name"));
+    }
+
+    [Test]
+    public void Parse_WithPostgreSqlPositionalParameters_ExtractsParameters()
+    {
+        // Arrange
+        var sql = "SELECT id, name FROM users WHERE user_id = $1 AND status = $2";
+
+        // Act
+        var queryBreakdown = QueryBreakdown.Parse(sql);
+
+        // Assert
+        Assert.That(queryBreakdown.Parameters.Count, Is.GreaterThanOrEqualTo(0));
+    }
+
+    [Test]
+    public void Parse_WithComplexQuery_ExtractsAllClauses()
+    {
+        // Arrange
+        var sql = @"
+            SELECT u.id, u.name, COUNT(o.id) AS order_count
+            FROM users u
+            LEFT JOIN orders o ON u.id = o.user_id
+            WHERE u.active = true
+            GROUP BY u.id, u.name
+            HAVING COUNT(o.id) > 0
+            ORDER BY order_count DESC
+        ";
+
+        // Act
+        var queryBreakdown = QueryBreakdown.Parse(sql);
+
+        // Assert
+        Assert.That(queryBreakdown.SelectClause.Clause, Is.Not.Empty);
+        Assert.That(queryBreakdown.FromClause.Clause, Is.Not.Empty);
+        Assert.That(queryBreakdown.WhereClause.Clause, Is.Not.Empty);
+        Assert.That(queryBreakdown.GroupByClause.Clause, Is.Not.Empty);
+        Assert.That(queryBreakdown.HavingClause.Clause, Is.Not.Empty);
+        Assert.That(queryBreakdown.OrderByClause.Clause, Is.Not.Empty);
+    }
+
+    [Test]
+    public void TryParse_WithValidSql_Succeeds()
+    {
+        // Arrange
+        var sql = "SELECT id, name FROM users";
+
+        // Act
+        var success = QueryBreakdown.TryParse(sql, out var queryBreakdown, out var errorMessage);
+
+        // Assert
+        Assert.That(success, Is.True);
+        Assert.That(queryBreakdown, Is.Not.Null);
+        Assert.That(errorMessage, Is.Empty);
+    }
+
+    [Test]
+    public void TryParse_WithEmptySql_ReturnsFalse()
+    {
+        // Arrange
+        var sql = "";
+
+        // Act
+        var success = QueryBreakdown.TryParse(sql, out var queryBreakdown, out var errorMessage);
+
+        // Assert
+        Assert.That(success, Is.False);
+        Assert.That(errorMessage, Is.Not.Empty);
+    }
+
+    #endregion
+
+    #region PostgreSQL-Specific Features Tests
+
+    [Test]
+    public void GetSql_WithDoubleQuotedIdentifiers_PreservesQuotes()
+    {
+        // Arrange
+        var queryBreakdown = new QueryBreakdown("\"Id\", \"Name\"", "\"Users\"");
+
+        // Act
+        var sql = queryBreakdown.GetSql();
+
+        // Assert
+        Assert.That(sql, Does.Contain("\""));
+    }
+
+    [Test]
+    public void Parse_WithDoubleQuotedIdentifiers_Succeeds()
+    {
+        // Arrange
+        var sql = "SELECT \"Id\", \"Name\" FROM \"Users\" WHERE \"Id\" = $1";
+
+        // Act
+        var queryBreakdown = QueryBreakdown.Parse(sql);
+
+        // Assert
+        Assert.That(queryBreakdown.SelectClause.Clause, Is.Not.Empty);
+        Assert.That(queryBreakdown.FromClause.Clause, Is.Not.Empty);
+    }
+
+    [Test]
+    public void Parse_WithLimitInOrderBy_ExtractsLimit()
+    {
+        // Arrange
+        var sql = "SELECT id, name FROM users ORDER BY id LIMIT 10";
+
+        // Act
+        var queryBreakdown = QueryBreakdown.Parse(sql);
+
+        // Assert
+        // LIMIT is appended to ORDER BY clause in PostgreSQL parsing
+        Assert.That(queryBreakdown.OrderByClause.Clause, Does.Contain("LIMIT").Or.Contain("Limit").Or.Contain("limit"));
+    }
+
+    [Test]
+    public void Parse_WithLimitAndOffset_ExtractsCorrectly()
+    {
+        // Arrange
+        var sql = "SELECT id, name FROM users ORDER BY id LIMIT 10 OFFSET 5";
+
+        // Act
+        var queryBreakdown = QueryBreakdown.Parse(sql);
+
+        // Assert
+        // Both LIMIT and OFFSET are appended to ORDER BY
+        Assert.That(queryBreakdown.OrderByClause.Clause, Is.Not.Empty);
+    }
+
+    #endregion
+
+    #region Edge Cases
+
+    [Test]
+    public void Constructor_DefaultConstructor_AllowsManualClauseAssignment()
+    {
+        // Arrange & Act
+        var queryBreakdown = new QueryBreakdown();
+        queryBreakdown.SelectClause.Clause = "id, name";
+        queryBreakdown.FromClause.Clause = "users";
+
+        // Assert
+        Assert.That(queryBreakdown.SelectClause.Clause, Is.EqualTo("id, name"));
+        Assert.That(queryBreakdown.FromClause.Clause, Is.EqualTo("users"));
+    }
+
+    [Test]
+    public void GetSql_EmptyQueryBreakdown_GeneratesBasicSelect()
+    {
+        // Arrange
+        var queryBreakdown = new QueryBreakdown();
+
+        // Act
+        var sql = queryBreakdown.GetSql();
+
+        // Assert
+        Assert.That(sql, Is.Not.Null);
+    }
+
+    #endregion
+
+    #region WITH Clause Tests
+
+    [Test]
+    public void AddWithClause_WithCTE_AddsToWithClauses()
+    {
+        // Arrange
+        var cte = new QueryBreakdown("id, name", "base_users");
+        var mainQuery = new QueryBreakdown("*", "active_users_cte");
+
+        // Act
+        mainQuery.AddWithClause("active_users_cte", cte);
+
+        // Assert
+        Assert.That(mainQuery.WithClauses, Has.Count.EqualTo(1));
+        Assert.That(mainQuery.WithClauses[0].TableName, Is.EqualTo("active_users_cte"));
+        Assert.That(mainQuery.WithClauses[0].Query, Is.EqualTo(cte));
+    }
+
+    [Test]
+    public void GetSql_WithSimpleCTE_GeneratesWithClause()
+    {
+        // Arrange
+        var cte = new QueryBreakdown("id, name", "base_users");
+        var mainQuery = new QueryBreakdown("*", "active_users_cte");
+        mainQuery.AddWithClause("active_users_cte", cte);
+
+        // Act
+        var sql = mainQuery.GetSql();
+
+        // Assert
+        Assert.That(sql, Contains.Substring("WITH"));
+        Assert.That(sql, Contains.Substring("active_users_cte AS"));
+        Assert.That(sql, Contains.Substring("id, name"));
+        Assert.That(sql, Contains.Substring("base_users"));
+    }
+
+    [Test]
+    public void GetSql_WithMultipleCTEs_GeneratesAllCTEs()
+    {
+        // Arrange
+        var cte1 = new QueryBreakdown("id, status", "users", "status = 'active'");
+        var cte2 = new QueryBreakdown("user_id, count(*)", "orders", "created >= CURRENT_DATE");
+
+        var mainQuery = new QueryBreakdown("*", "results");
+        mainQuery.AddWithClause("active_users", cte1);
+        mainQuery.AddWithClause("recent_orders", cte2);
+
+        // Act
+        var sql = mainQuery.GetSql();
+
+        // Assert
+        Assert.That(sql, Contains.Substring("WITH"));
+        Assert.That(sql, Contains.Substring("active_users AS"));
+        Assert.That(sql, Contains.Substring("recent_orders AS"));
+    }
+
+    #endregion
+
+    #region CTE Parameter Inheritance Tests - PostgreSQL
+
+    [Test]
+    public void GetMergedParameters_WithNoCTEs_ReturnsMainQueryParameters()
+    {
+        // Arrange
+        var query = new QueryBreakdown("*", "USERS");
+        query.AddParameter("UserId", 123);
+        query.AddParameter("ActiveStatus", true);
+
+        // Act
+        var merged = query.GetMergedParameters();
+
+        // Assert
+        // PostgreSQL stores parameters with positional and name-based formats
+        Assert.That(merged.Count, Is.GreaterThanOrEqualTo(2));
+        var keys = merged.Keys.ToList();
+        Assert.That(keys.Any(k => k.Contains("UserId")));
+        Assert.That(keys.Any(k => k.Contains("ActiveStatus")));
+    }
+
+    [Test]
+    public void GetMergedParameters_WithSingleCTE_MergesParameters()
+    {
+        // Arrange
+        var cte = new QueryBreakdown("ID, NAME", "BASE_USERS", "ACTIVE = true");
+        cte.AddParameter("MinDate", DateTime.Today.AddDays(-30));
+
+        var mainQuery = new QueryBreakdown("*", "ACTIVE_USERS");
+        mainQuery.AddParameter("ResultLimit", 100);
+        mainQuery.AddWithClause("ACTIVE_USERS", cte);
+
+        // Act
+        var merged = mainQuery.GetMergedParameters();
+
+        // Assert
+        var keys = merged.Keys.ToList();
+        Assert.That(keys.Any(k => k.Contains("MinDate")));
+        Assert.That(keys.Any(k => k.Contains("ResultLimit")));
+    }
+
+    [Test]
+    public void GetMergedParameters_WithMultipleCTEs_MergesAllParameters()
+    {
+        // Arrange
+        var cte1 = new QueryBreakdown("ID, STATUS", "USERS", "STATUS = 'active'");
+        cte1.AddParameter("Status1", "active");
+
+        var cte2 = new QueryBreakdown("USER_ID, CREATED", "ORDERS", "CREATED >= CURRENT_DATE");
+        cte2.AddParameter("MinDate", DateTime.Today.AddDays(-30));
+
+        var mainQuery = new QueryBreakdown("*", "RESULTS");
+        mainQuery.AddParameter("ResultLimit", 50);
+        mainQuery.AddWithClause("ACTIVE_USERS", cte1);
+        mainQuery.AddWithClause("RECENT_ORDERS", cte2);
+
+        // Act
+        var merged = mainQuery.GetMergedParameters();
+
+        // Assert
+        var keys = merged.Keys.ToList();
+        Assert.That(keys.Any(k => k.Contains("Status1")));
+        Assert.That(keys.Any(k => k.Contains("MinDate")));
+        Assert.That(keys.Any(k => k.Contains("ResultLimit")));
+    }
+
+    [Test]
+    public void GetMergedParameters_WithParameterConflict_MainQueryTakesPrecedence()
+    {
+        // Arrange
+        var cte = new QueryBreakdown("ID, NAME", "BASE_USERS");
+        cte.AddParameter("UserId", 999); // CTE version
+
+        var mainQuery = new QueryBreakdown("*", "ACTIVE_USERS");
+        mainQuery.AddParameter("UserId", 123); // Main query version (should win)
+        mainQuery.AddWithClause("ACTIVE_USERS", cte);
+
+        // Act
+        var merged = mainQuery.GetMergedParameters();
+
+        // Assert
+        // Find the UserId parameter value
+        var userIdKey = merged.Keys.FirstOrDefault(k => k.Contains("UserId") && !k.Contains("$"));
+        Assert.That(userIdKey, Is.Not.Null);
+        Assert.That(merged[userIdKey], Is.EqualTo(123)); // Main query value, not CTE value
+    }
+
+    [Test]
+    public void GetMergedParameters_WithNestedCTEs_CollectsAllParameters()
+    {
+        // Arrange
+        var cte1 = new QueryBreakdown("id, name", "base_users");
+        cte1.AddParameter("Status", "active");
+
+        var cte2 = new QueryBreakdown("*", "NESTED_USERS");
+        cte2.AddParameter("Level", 1);
+        cte2.AddWithClause("ACTIVE_USERS", cte1);
+
+        var mainQuery = new QueryBreakdown("*", "FINAL_RESULTS");
+        mainQuery.AddParameter("Limit", 100);
+        mainQuery.AddWithClause("FILTERED_USERS", cte2);
+
+        // Act
+        var merged = mainQuery.GetMergedParameters();
+
+        // Assert
+        var keys = merged.Keys.ToList();
+        Assert.That(keys.Any(k => k.Contains("Status")), "Should include Status from nested CTE");
+        Assert.That(keys.Any(k => k.Contains("Level")), "Should include Level from middle CTE");
+        Assert.That(keys.Any(k => k.Contains("Limit")), "Should include Limit from main query");
+    }
+
+    [Test]
+    public void GetMergedParameters_PreservesParameterTypes()
+    {
+        // Arrange
+        var cte = new QueryBreakdown("id, name", "users");
+        cte.AddParameter("CreatedDate", new DateTime(2024, 1, 1));
+
+        var mainQuery = new QueryBreakdown("*", "results");
+        mainQuery.AddParameter("IsActive", true);
+        mainQuery.AddParameter("Threshold", 42.5);
+        mainQuery.AddWithClause("users_cte", cte);
+
+        // Act
+        var merged = mainQuery.GetMergedParameters();
+
+        // Assert
+        var dateKey = merged.Keys.FirstOrDefault(k => k.Contains("CreatedDate") && !k.Contains("$"));
+        var boolKey = merged.Keys.FirstOrDefault(k => k.Contains("IsActive") && !k.Contains("$"));
+        var doubleKey = merged.Keys.FirstOrDefault(k => k.Contains("Threshold") && !k.Contains("$"));
+
+        Assert.That(dateKey, Is.Not.Null);
+        Assert.That(merged[dateKey], Is.TypeOf<DateTime>());
+
+        Assert.That(boolKey, Is.Not.Null);
+        Assert.That(merged[boolKey], Is.TypeOf<bool>());
+
+        Assert.That(doubleKey, Is.Not.Null);
+        Assert.That(merged[doubleKey], Is.TypeOf<double>());
+    }
+
+    #endregion
+}

tests/Strata.SqlTools.PostgreSql.Tests/PostgreSql/RecursiveCTETests.cs

@@ -0,0 +1,319 @@
+using Strata.SqlTools.Breakdowns.PostgreSql;
+using Strata.SqlTools.SqlBreakdown.Classes;
+
+namespace Strata.SqlTools.SqlBreakdown.Tests.PostgreSql;
+
+[TestFixture]
+public class RecursiveCTETests
+{
+    #region Recursive CTE Structure Tests
+
+    [Test]
+    public void RecursiveCTE_WithIsRecursiveTrue_CreatesRecursiveStructure()
+    {
+        // Arrange
+        var anchorQuery = new QueryBreakdown(
+            "employee_id, manager_id, name, 1 as level",
+            "employees",
+            "manager_id IS NULL"
+        );
+
+        var recursiveQuery = new QueryBreakdown(
+            "e.employee_id, e.manager_id, e.name, org.level + 1",
+            "employees e INNER JOIN org_hierarchy org ON e.manager_id = org.employee_id"
+        );
+
+        var withClause = new WithClause("org_hierarchy", anchorQuery)
+        {
+            IsRecursive = true,
+            RecursiveQuery = recursiveQuery
+        };
+
+        // Act
+        var isRecursive = withClause.IsRecursive;
+        var hasRecursiveQuery = withClause.RecursiveQuery != null;
+
+        // Assert
+        Assert.That(isRecursive, Is.True);
+        Assert.That(hasRecursiveQuery, Is.True);
+    }
+
+    [Test]
+    public void GetSql_WithRecursiveCTE_GeneratesRecursiveKeyword()
+    {
+        // Arrange
+        var anchorQuery = new QueryBreakdown("id, manager_id, name, 1 as level", "employees", "manager_id IS NULL");
+        var recursiveQuery = new QueryBreakdown(
+            "e.id, e.manager_id, e.name, h.level + 1",
+            "employees e INNER JOIN org_hierarchy h ON e.manager_id = h.id"
+        );
+
+        var mainQuery = new QueryBreakdown("*", "org_hierarchy");
+        var withClause = new WithClause("org_hierarchy", anchorQuery)
+        {
+            IsRecursive = true,
+            RecursiveQuery = recursiveQuery
+        };
+        mainQuery.AddWithClause(withClause);
+
+        // Act
+        var sql = mainQuery.GetSql();
+
+        // Assert
+        Assert.That(sql, Contains.Substring("WITH RECURSIVE"), "SQL should contain WITH RECURSIVE keyword");
+    }
+
+    [Test]
+    public void GetSql_WithRecursiveCTE_ContainsUnionAll()
+    {
+        // Arrange
+        var anchorQuery = new QueryBreakdown("id, parent_id, value", "nodes", "parent_id IS NULL");
+        var recursiveQuery = new QueryBreakdown(
+            "c.id, c.parent_id, c.value",
+            "nodes c INNER JOIN tree t ON c.parent_id = t.id"
+        );
+
+        var mainQuery = new QueryBreakdown("*", "tree");
+        var withClause = new WithClause("tree", anchorQuery)
+        {
+            IsRecursive = true,
+            RecursiveQuery = recursiveQuery
+        };
+        mainQuery.AddWithClause(withClause);
+
+        // Act
+        var sql = mainQuery.GetSql();
+
+        // Assert
+        Assert.That(sql, Contains.Substring("UNION ALL"), "Recursive CTE should contain UNION ALL");
+    }
+
+    [Test]
+    public void GetSql_WithNonRecursiveCTE_DoesNotGenerateRecursiveKeyword()
+    {
+        // Arrange
+        var cte = new QueryBreakdown("id, name", "employees", "status = 'active'");
+        var mainQuery = new QueryBreakdown("*", "active_employees");
+
+        var withClause = new WithClause("active_employees", cte)
+        {
+            IsRecursive = false  // Explicitly non-recursive
+        };
+        mainQuery.AddWithClause(withClause);
+
+        // Act
+        var sql = mainQuery.GetSql();
+
+        // Assert
+        Assert.That(sql, Contains.Substring("WITH"), "SQL should contain WITH keyword");
+        Assert.That(sql, Does.Not.Contain("WITH RECURSIVE"), "Non-recursive CTE should not have RECURSIVE keyword");
+    }
+
+    #endregion
+
+    #region Recursive CTE Parameter Tests
+
+    [Test]
+    public void GetMergedParameters_WithRecursiveCTE_MergesAnchorAndRecursiveParams()
+    {
+        // Arrange
+        var anchorQuery = new QueryBreakdown("id, manager_id, name", "employees", "manager_id IS NULL");
+        anchorQuery.AddParameter("AnchorStatus", "active");
+
+        var recursiveQuery = new QueryBreakdown(
+            "e.id, e.manager_id, e.name",
+            "employees e INNER JOIN org_hierarchy h ON e.manager_id = h.id",
+            "e.status = 'active'"
+        );
+        recursiveQuery.AddParameter("RecursiveLevel", 10);
+        recursiveQuery.AddParameter("RecursiveStatus", "active");
+
+        var mainQuery = new QueryBreakdown("*", "org_hierarchy");
+        mainQuery.AddParameter("MainLimit", 100);
+
+        var withClause = new WithClause("org_hierarchy", anchorQuery)
+        {
+            IsRecursive = true,
+            RecursiveQuery = recursiveQuery
+        };
+        mainQuery.AddWithClause(withClause);
+
+        // Act
+        var merged = mainQuery.GetMergedParameters();
+
+        // Assert
+        var keys = merged.Keys.ToList();
+        Assert.That(keys.Any(k => k.Contains("AnchorStatus")), "Should include anchor query parameters");
+        Assert.That(keys.Any(k => k.Contains("RecursiveLevel")), "Should include recursive query parameters");
+        Assert.That(keys.Any(k => k.Contains("RecursiveStatus")), "Should include recurring query parameters");
+        Assert.That(keys.Any(k => k.Contains("MainLimit")), "Should include main query parameters");
+    }
+
+    [Test]
+    [Ignore("Pre-existing: parameter key search needs refinement for positional $ parameters")]
+    public void GetMergedParameters_WithRecursiveCTE_MainQueryParamTakesPrecedence()
+    {
+        // Arrange
+        var anchorQuery = new QueryBreakdown("id, name", "employees");
+        anchorQuery.AddParameter("Status", "inactive"); // CTE version
+
+        var recursiveQuery = new QueryBreakdown("e.id, e.name", "employees e");
+        recursiveQuery.AddParameter("Status", "inactive"); // Recursive version
+
+        var mainQuery = new QueryBreakdown("*", "hierarchy");
+        mainQuery.AddParameter("Status", "active"); // Main query version (should win)
+
+        var withClause = new WithClause("hierarchy", anchorQuery)
+        {
+            IsRecursive = true,
+            RecursiveQuery = recursiveQuery
+        };
+        mainQuery.AddWithClause(withClause);
+
+        // Act
+        var merged = mainQuery.GetMergedParameters();
+
+        // Assert
+        // PostgreSQL stores parameters with positional syntax
+        var statusKey = merged.Keys.FirstOrDefault(k => k.Contains("Status") && !k.StartsWith("$"));
+        Assert.That(statusKey, Is.Not.Null);
+        Assert.That(merged[statusKey], Is.EqualTo("active"), "Main query parameter should take precedence");
+    }
+
+    #endregion
+
+    #region Complex Recursive CTE Tests
+
+    [Test]
+    public void GetSql_WithMultipleRecursiveCTEs_GeneratesAllRecursiveClauses()
+    {
+        // Arrange
+        // First recursive CTE: Employee hierarchy
+        var emp_anchor = new QueryBreakdown("id, manager_id, name, 1 as level", "employees", "manager_id IS NULL");
+        var emp_recursive = new QueryBreakdown(
+            "e.id, e.manager_id, e.name, h.level + 1",
+            "employees e INNER JOIN emp_hierarchy h ON e.manager_id = h.id"
+        );
+        var emp_withClause = new WithClause("emp_hierarchy", emp_anchor)
+        {
+            IsRecursive = true,
+            RecursiveQuery = emp_recursive
+        };
+
+        // Second CTE: Department hierarchy (non-recursive)
+        var dept_cte = new QueryBreakdown("id, name", "departments", "active = 1");
+        var dept_withClause = new WithClause("dept_list", dept_cte)
+        {
+            IsRecursive = false
+        };
+
+        var mainQuery = new QueryBreakdown("*", "results");
+        mainQuery.AddWithClause(emp_withClause);
+        mainQuery.AddWithClause(dept_withClause);
+
+        // Act
+        var sql = mainQuery.GetSql();
+
+        // Assert
+        Assert.That(sql, Contains.Substring("WITH RECURSIVE"), "Should have RECURSIVE keyword for mixed CTEs");
+        Assert.That(sql, Contains.Substring("emp_hierarchy AS"), "Should have first CTE");
+        Assert.That(sql, Contains.Substring("dept_list AS"), "Should have second CTE");
+    }
+
+    [Test]
+    public void RecursiveCTE_WithMixedRecursiveAndNonRecursive_MixedStructureWorks()
+    {
+        // Arrange
+        var nonRecursiveCte = new QueryBreakdown("id, name", "base_data");
+        var withClause1 = new WithClause("base", nonRecursiveCte) { IsRecursive = false };
+
+        var anchor = new QueryBreakdown("id, parent_id", "tree_data", "parent_id IS NULL");
+        var recursive = new QueryBreakdown(
+            "t.id, t.parent_id",
+            "tree_data t INNER JOIN tree_hierarchy h ON t.parent_id = h.id"
+        );
+        var withClause2 = new WithClause("tree_hierarchy", anchor)
+        {
+            IsRecursive = true,
+            RecursiveQuery = recursive
+        };
+
+        var mainQuery = new QueryBreakdown("*", "results");
+        mainQuery.AddWithClause(withClause1);
+        mainQuery.AddWithClause(withClause2);
+
+        // Act
+        var sql = mainQuery.GetSql();
+
+        // Assert
+        Assert.That(sql, Contains.Substring("WITH RECURSIVE"));
+        Assert.That(sql.Contains("base AS"), "Non-recursive CTE should be included");
+        Assert.That(sql.Contains("tree_hierarchy AS"), "Recursive CTE should be included");
+    }
+
+    [Test]
+    public void RecursiveCTE_WithoutRecursiveQuery_UsesOnlyAnchor()
+    {
+        // Arrange
+        var anchorQuery = new QueryBreakdown("id, name", "employees");
+        var withClause = new WithClause("employees_cte", anchorQuery)
+        {
+            IsRecursive = true,
+            RecursiveQuery = null  // No recursive query provided
+        };
+
+        var mainQuery = new QueryBreakdown("*", "results");
+        mainQuery.AddWithClause(withClause);
+
+        // Act
+        var sql = mainQuery.GetSql();
+
+        // Assert
+        // Should still generate WITH RECURSIVE (IsRecursive = true)
+        // but only include the anchor query
+        Assert.That(sql, Contains.Substring("WITH RECURSIVE"));
+        Assert.That(sql, Contains.Substring("employees_cte AS"));
+    }
+
+    #endregion
+
+    #region Recursive CTE Edge Cases
+
+    [Test]
+    public void RecursiveCTE_IsRecursiveProperty_CanBeToggled()
+    {
+        // Arrange
+        var cte = new QueryBreakdown("id, name", "data");
+        var withClause = new WithClause("cte_name", cte);
+
+        // Act & Assert
+        Assert.That(withClause.IsRecursive, Is.False, "Default should be non-recursive");
+
+        withClause.IsRecursive = true;
+        Assert.That(withClause.IsRecursive, Is.True, "Should be toggleable to recursive");
+
+        withClause.IsRecursive = false;
+        Assert.That(withClause.IsRecursive, Is.False, "Should be toggleable back to non-recursive");
+    }
+
+    [Test]
+    public void RecursiveCTE_RecursiveQueryProperty_CanBeSet()
+    {
+        // Arrange
+        var anchor = new QueryBreakdown("id, parent", "data");
+        var recursive = new QueryBreakdown("c.id, c.parent", "data c INNER JOIN tree h ON c.parent = h.id");
+
+        var withClause = new WithClause("tree", anchor);
+
+        // Act
+        Assert.That(withClause.RecursiveQuery, Is.Null, "Should start as null");
+
+        withClause.IsRecursive = true;
+        withClause.RecursiveQuery = recursive;
+
+        // Assert
+        Assert.That(withClause.RecursiveQuery, Is.EqualTo(recursive));
+    }
+
+    #endregion
+}

tests/Strata.SqlTools.PostgreSql.Tests/PostgreSql/StatementExpressionParserTests.cs

@@ -0,0 +1,357 @@
+using Strata.SqlTools.Statements.PostgreSql;
+
+namespace Strata.SqlTools.SqlBreakdown.Tests.PostgreSql;
+
+[TestFixture]
+public class StatementExpressionParserTests
+{
+    [Test]
+    public void Parse_NumberExpression_ReturnNum()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "42";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_NegativeNumber_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "-42";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_DecimalNumber_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "3.14159";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_StringExpression_ReturnsString()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "'hello world'";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_StringWithEscapedQuotes_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "'it''s working'"; // PostgreSQL escape style
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_ColumnIdentifier_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "user_id";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_QuotedIdentifier_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "\"UserId\"";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_ColumnWithTablePrefix_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "users.id";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_QuotedColumnWithTablePrefix_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "\"Users\".\"Id\"";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_SimpleAddition_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "42 + 8";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_SimpleSubtraction_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "42 - 8";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_SimpleMultiplication_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "42 * 8";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_SimpleDivision_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "42 / 8";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_ComplexArithmeticExpression_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "(42 + 8) * (10 - 2) / 4";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_FunctionCall_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "COUNT(id)";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_CountExpression_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "COUNT(*)";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_SumExpression_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "SUM(amount)";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_CaseInsensitiveFunctionName_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "sum(amount)";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_FunctionWithMultipleArguments_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "SUBSTRING(name, 1, 10)";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_NestedFunctionCalls_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "UPPER(SUBSTRING(name, 1, 10))";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_ColumnWithAlias_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "COUNT(id) AS total_count";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_CaseExpression_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "CASE WHEN status = 'active' THEN 1 ELSE 0 END";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_PostgreSqlPositionalParameter_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "$1";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_NamedParameter_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = "@userId";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+
+    [Test]
+    public void Parse_ColonNamedParameter_Succeeds()
+    {
+        // Arrange
+        var parser = new StatementExpressionParser();
+        var sql = ":userId";
+
+        // Act
+        var result = parser.Parse(sql);
+
+        // Assert
+        Assert.That(result, Is.Not.Null);
+    }
+}

tests/Strata.SqlTools.PostgreSql.Tests/PostgreSql/StatementReaderTests.cs

@@ -0,0 +1,223 @@
+using Strata.SqlTools.SqlBreakdown.Enums.SQL;
+using Strata.SqlTools.SqlBreakdown.Exceptions;
+using Strata.SqlTools.SqlBreakdown.Exceptions;
+using StatementReader = Strata.SqlTools.Statements.PostgreSql.StatementReader;
+
+namespace Strata.SqlTools.SqlBreakdown.Tests.PostgreSql;
+
+[TestFixture]
+public class StatementReaderTests
+{
+    [Test]
+    public void StatementReader_ParsesCalculationString()
+    {
+        // Arrange
+        var calculationString = "(1 + 2) / SUM(column_id) + SUM(other_column) - SUM(another_column) * 2.3";
+        var sqlReader = new StatementReader(calculationString);
+        var tokens = new List<(TokenType Type, string Value)>();
+
+        // Act
+        while (sqlReader.Read())
+        {
+            tokens.Add((sqlReader.TokenType, sqlReader.TokenValue));
+        }
+
+        // Assert
+        Assert.That(tokens, Is.Not.Empty);
+        Assert.That(tokens[0].Type, Is.EqualTo(TokenType.LeftParenthesis));
+        Assert.That(tokens[1].Type, Is.EqualTo(TokenType.Number));
+        Assert.That(tokens[1].Value, Is.EqualTo("1"));
+    }
+
+    [Test]
+    public void StatementReader_ParsesDoubleQuotedIdentifiers()
+    {
+        // Arrange - PostgreSQL-specific double-quoted identifiers (case-sensitive)
+        var calculationString = "\"COLUMN_1\" + \"COLUMN_2\" * 2";
+        var sqlReader = new StatementReader(calculationString);
+        var tokens = new List<(TokenType Type, string Value)>();
+
+        // Act
+        while (sqlReader.Read())
+        {
+            tokens.Add((sqlReader.TokenType, sqlReader.TokenValue));
+        }
+
+        // Assert
+        Assert.That(tokens, Has.Count.EqualTo(5)); // "COLUMN_1" + "COLUMN_2" * 2
+        Assert.That(tokens[0].Type, Is.EqualTo(TokenType.ColumnIdentifier));
+        Assert.That(tokens[0].Value, Is.EqualTo("COLUMN_1"));
+        Assert.That(tokens[1].Type, Is.EqualTo(TokenType.Plus));
+        Assert.That(tokens[2].Type, Is.EqualTo(TokenType.ColumnIdentifier));
+    }
+
+    [Test]
+    public void StatementReader_ParsesDoubleQuotedIdentifiersWithCase()
+    {
+        // Arrange - PostgreSQL preserves case in double-quoted identifiers
+        var calculationString = "\"MyColumn\" + \"AnotherColumn\"";
+        var sqlReader = new StatementReader(calculationString);
+        var tokens = new List<(TokenType Type, string Value)>();
+
+        // Act
+        while (sqlReader.Read())
+        {
+            tokens.Add((sqlReader.TokenType, sqlReader.TokenValue));
+        }
+
+        // Assert
+        Assert.That(tokens[0].Type, Is.EqualTo(TokenType.ColumnIdentifier));
+        Assert.That(tokens[0].Value, Is.EqualTo("MyColumn"));
+        Assert.That(tokens[2].Type, Is.EqualTo(TokenType.ColumnIdentifier));
+        Assert.That(tokens[2].Value, Is.EqualTo("AnotherColumn"));
+    }
+
+    [Test]
+    public void StatementReader_ParsesPositionalParameters()
+    {
+        // Arrange - PostgreSQL positional parameters ($1, $2, etc.)
+        var calculationString = "column_id = $1 AND status = $2";
+        var sqlReader = new StatementReader(calculationString);
+        var tokens = new List<(TokenType Type, string Value)>();
+
+        // Act
+        while (sqlReader.Read())
+        {
+            tokens.Add((sqlReader.TokenType, sqlReader.TokenValue));
+        }
+
+        // Assert
+        Assert.That(tokens.Count, Is.GreaterThan(0));
+        var paramTokens = tokens.Where(t => t.Type == TokenType.Parameter).ToList();
+        Assert.That(paramTokens.Count, Is.EqualTo(2));
+        Assert.That(paramTokens[0].Value, Is.EqualTo("$1"));
+        Assert.That(paramTokens[1].Value, Is.EqualTo("$2"));
+    }
+
+    [Test]
+    public void StatementReader_ParsesUnderscorePrefixedIdentifiers()
+    {
+        // Arrange - PostgreSQL allows underscores to start identifiers
+        var calculationString = "_internal_column + _private_field";
+        var sqlReader = new StatementReader(calculationString);
+        var tokens = new List<(TokenType Type, string Value)>();
+
+        // Act
+        while (sqlReader.Read())
+        {
+            tokens.Add((sqlReader.TokenType, sqlReader.TokenValue));
+        }
+
+        // Assert
+        var identifierTokens = tokens.Where(t => t.Type == TokenType.ColumnIdentifier).ToList();
+        Assert.That(identifierTokens.Count, Is.GreaterThanOrEqualTo(2));
+    }
+
+    [Test]
+    public void StatementReader_ParsesComplexExpression()
+    {
+        // Arrange - Complex PostgreSQL expression
+        var calculationString = "(\"Price\" * quantity) - discount WHERE user_id = $1";
+        var sqlReader = new StatementReader(calculationString);
+        var tokens = new List<(TokenType Type, string Value)>();
+
+        // Act
+        while (sqlReader.Read())
+        {
+            tokens.Add((sqlReader.TokenType, sqlReader.TokenValue));
+        }
+
+        // Assert
+        Assert.That(tokens, Is.Not.Empty);
+        var identifierCount = tokens.Count(t => t.Type == TokenType.ColumnIdentifier);
+        Assert.That(identifierCount, Is.GreaterThan(0));
+    }
+
+    [Test]
+    public void StatementReader_ThrowsOnUnclosedDoubleQuote()
+    {
+        // Arrange
+        var calculationString = "\"UNCLOSED_IDENTIFIER + 1";
+        var sqlReader = new StatementReader(calculationString);
+
+        // Act & Assert
+        Assert.Throws<InvalidSyntaxException>(() =>
+        {
+            while (sqlReader.Read()) { }
+        });
+    }
+
+    [Test]
+    public void StatementReader_ParsesWhitespace()
+    {
+        // Arrange
+        var calculationString = "  column_1   +   column_2  ";
+        var sqlReader = new StatementReader(calculationString);
+        var tokens = new List<(TokenType Type, string Value)>();
+
+        // Act
+        while (sqlReader.Read())
+        {
+            tokens.Add((sqlReader.TokenType, sqlReader.TokenValue));
+        }
+
+        // Assert
+        Assert.That(tokens.Count, Is.GreaterThan(0));
+    }
+
+    [Test]
+    public void StatementReader_ParsesOperators()
+    {
+        // Arrange
+        var calculationString = "a = b";
+        var sqlReader = new StatementReader(calculationString);
+        var tokens = new List<(TokenType Type, string Value)>();
+
+        // Act
+        while (sqlReader.Read())
+        {
+            tokens.Add((sqlReader.TokenType, sqlReader.TokenValue));
+        }
+
+        // Assert
+        Assert.That(tokens.Count, Is.GreaterThan(0));
+    }
+
+    [Test]
+    public void StatementReader_ParsesStrings()
+    {
+        // Arrange
+        var calculationString = "column = 'string value' AND other = 'another string'";
+        var sqlReader = new StatementReader(calculationString);
+        var tokens = new List<(TokenType Type, string Value)>();
+
+        // Act
+        while (sqlReader.Read())
+        {
+            tokens.Add((sqlReader.TokenType, sqlReader.TokenValue));
+        }
+
+        // Assert
+        var stringTokens = tokens.Where(t => t.Type == TokenType.String).ToList();
+        Assert.That(stringTokens.Count, Is.GreaterThanOrEqualTo(2));
+    }
+
+    [Test]
+    public void StatementReader_ParsesNumbers()
+    {
+        // Arrange
+        var calculationString = "42 + 3.14 - 100";
+        var sqlReader = new StatementReader(calculationString);
+        var tokens = new List<(TokenType Type, string Value)>();
+
+        // Act
+        while (sqlReader.Read())
+        {
+            tokens.Add((sqlReader.TokenType, sqlReader.TokenValue));
+        }
+
+        // Assert
+        var numberTokens = tokens.Where(t => t.Type == TokenType.Number).ToList();
+        Assert.That(numberTokens.Count, Is.GreaterThan(0));
+    }
+}

tests/Strata.SqlTools.PostgreSql.Tests/Strata.SqlTools.PostgreSql.Tests.csproj

@@ -0,0 +1,29 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <LangVersion>latest</LangVersion>
+
+    <IsPackable>false</IsPackable>
+    <IsTestProject>true</IsTestProject>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" Version="6.0.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
+    <PackageReference Include="NUnit" Version="3.14.0" />
+    <PackageReference Include="NUnit.Analyzers" Version="3.9.0" />
+    <PackageReference Include="NUnit3TestAdapter" Version="4.5.0" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="NUnit.Framework" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\Strata.SqlTools.PostgreSql\Strata.SqlTools.PostgreSql.csproj" />
+  </ItemGroup>
+
+</Project>