LangChain provides SQLDatabaseToolkit and SQL Agent capabilities for building text-to-SQL applications with LLM orchestration. Open-source (MIT license) Python and JavaScript libraries. The SQLDatabaseToolkit wraps database connections with tools for schema introspection, query execution, and error handling that LLMs can use autonomously. SQL Agent provides ReAct-style reasoning—the LLM iteratively explores schema, generates queries, executes them, and refines based on results. Supports PostgreSQL, MySQL, SQLite, SQL Server, and any SQLAlchemy-compatible database. Key components include SQLDatabase (connection wrapper), QuerySQLDataBaseTool (query execution), InfoSQLDatabaseTool (schema retrieval), and ListSQLDatabaseTool (table listing). Few-shot example injection and custom prompting enable accuracy improvements. Integration with vector stores enables RAG-enhanced query generation. For production: combine with LangSmith for tracing and evaluation. Page should cover: SQLDatabaseToolkit setup tutorial, SQL Agent architecture, few-shot example configuration, RAG integration patterns, error handling strategies, comparison with LlamaIndex, and production deployment considerations.