LangChain SQL Tools

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.