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docs/fluent-builder-api.md

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+# Fluent Builder API
+
+The fluent API is built around interfaces like `IDynamicSelectQueryBuilder`, `IDynamicInsertQueryBuilder`, `IDynamicUpdateQueryBuilder`, and `IDynamicDeleteQueryBuilder`.
+
+## Core Select Flow
+
+```csharp
+using (var query = db.From("users", "u")
+    .Where("u.id", 19)
+    .SelectColumn("u.first", "u.last"))
+{
+    var result = query.Execute().ToList();
+}
+```
+
+## Typed Select
+
+```csharp
+using (var query = db.From<User>("u")
+    .Where(x => x.u.id == 19)
+    .Select(x => x.u.All()))
+{
+    var users = query.Execute<User>().ToList();
+}
+```
+
+## Parser Lambda Patterns
+
+The parser supports patterns tested in `DynamORM.Tests/Select/ParserTests.cs`:
+
+- `From(x => x.dbo.Users)`
+- `From(x => x.dbo.Users.As(x.u))`
+- `Join(x => x.Left().Accounts.As(x.a).On(x.a.userId == x.u.id))`
+- `Where(x => x.Or(x.u.id > 100))`
+- `Select(x => x.u.first.As(x.firstName))`
+- `GroupBy(x => x.u.last)`
+- `Having(x => x.Count() > 1)`
+- `OrderBy(x => x.u.id.Desc())`
+
+## Subqueries
+
+```csharp
+var sub = new DynamicSelectQueryBuilder(db).From(x => x.dbo.Users);
+
+using (var query = new DynamicSelectQueryBuilder(db)
+    .From(x => x(sub).As("u"))
+    .Select(x => x.u.All()))
+{
+    var rows = query.Execute().ToList();
+}
+```
+
+## Scalar Helpers
+
+```csharp
+var count = db.From<User>()
+    .Select(x => x.Count())
+    .ScalarAs<int>();
+```
+
+## Modify Builders
+
+```csharp
+db.Insert("users").Values("code", "301").Values("first", "Ada").Execute();
+
+db.Update("users")
+    .Values("first", "Alicia")
+    .Where("id", 301)
+    .Execute();
+
+db.Delete("users")
+    .Where("id", 301)
+    .Execute();
+```
+
+## SQL Inspection
+
+You can inspect generated SQL from builder objects:
+
+```csharp
+var sql = query.CommandText();
+```
+
+Command text assertions are heavily used in parser tests.