CSharpDB.Sql 1.2.0

CSharpDB.Sql

SQL tokenizer, recursive-descent parser, and abstract syntax tree (AST) for the CSharpDB embedded database engine.

Overview

CSharpDB.Sql provides a complete SQL front-end: a single-pass tokenizer, a recursive-descent parser, and a rich AST hierarchy. It transforms SQL text into strongly-typed statement and expression objects that downstream components (query planner, execution engine) consume. Zero external dependencies.

Features

• 108 token types covering SQL keywords, literals, identifiers, @parameters, operators, and punctuation
• Full DDL/DML parsing: CREATE/DROP/ALTER TABLE, CREATE/DROP INDEX, CREATE/DROP VIEW, CREATE/DROP TRIGGER
• Rich query support: SELECT with JOINs (INNER, LEFT, RIGHT, CROSS), WHERE, GROUP BY, HAVING, ORDER BY, LIMIT/OFFSET, CTEs (WITH)
• Expression tree: binary/unary operators, LIKE, IN, BETWEEN, IS NULL, aggregate functions (COUNT, SUM, AVG, MIN, MAX with DISTINCT)
• Fast-path optimizers: TryParseSimpleSelect and TryParseSimplePrimaryKeyLookup detect common patterns and skip full AST construction

Usage

using CSharpDB.Sql;

// Parse a SQL statement
var statements = Parser.Parse("SELECT id, name FROM users WHERE age > 21");

// The result is a list of strongly-typed AST nodes
if (statements[0] is SelectStatement select)
{
    Console.WriteLine($"Table: {select.From}");
    Console.WriteLine($"Columns: {select.Columns.Count}");
    Console.WriteLine($"Has WHERE: {select.Where != null}");
}

// Parse DDL
var ddl = Parser.Parse("""
    CREATE TABLE orders (
        id INTEGER PRIMARY KEY,
        user_id INTEGER,
        total REAL
    )
    """);

// Fast-path detection for simple queries
if (Parser.TryParseSimplePrimaryKeyLookup(sql, out var lookup))
{
    // Skip full parsing for SELECT ... WHERE pk = value
}

AST Hierarchy

Statements: CreateTableStatement, DropTableStatement, InsertStatement, SelectStatement, UpdateStatement, DeleteStatement, AlterTableStatement, CreateIndexStatement, DropIndexStatement, CreateViewStatement, DropViewStatement, CreateTriggerStatement, DropTriggerStatement, WithStatement

Expressions: LiteralExpression, ParameterExpression, ColumnRefExpression, BinaryExpression, UnaryExpression, LikeExpression, InExpression, BetweenExpression, IsNullExpression, FunctionCallExpression

Table References: SimpleTableRef, JoinTableRef (Inner, LeftOuter, RightOuter, Cross)

Installation

dotnet add package CSharpDB.Sql

Dependencies

• CSharpDB.Core - shared type system and schema definitions

Related Packages

License

MIT - see LICENSE for details.