Loading from databases in LangChain

Introduction

Loading data from databases lets your program use stored information easily. It helps you work with big data saved in one place.

You want to get user info saved in a database to show on a website.

You need to analyze sales data stored in a database for reports.

You want to load chat history saved in a database for a chatbot.

You need to fetch product details from a database to display in an app.

Syntax

LangChain

from langchain.document_loaders import SQLDatabaseLoader

loader = SQLDatabaseLoader(
    database_uri="sqlite:///path_to_your_database.db",
    sql_query="SELECT * FROM your_table"
)
documents = loader.load()

The SQLDatabaseLoader connects to your database using the URI.

You provide a SQL query to select the data you want to load.

Examples

This loads the name and age columns from the users table.

LangChain

from langchain.document_loaders import SQLDatabaseLoader

loader = SQLDatabaseLoader(
    database_uri="sqlite:///mydata.db",
    sql_query="SELECT name, age FROM users"
)
docs = loader.load()

This loads all pending orders from a PostgreSQL database.

LangChain

from langchain.document_loaders import SQLDatabaseLoader

loader = SQLDatabaseLoader(
    database_uri="postgresql://user:pass@localhost/dbname",
    sql_query="SELECT * FROM orders WHERE status='pending'"
)
docs = loader.load()

Sample Program

This program connects to a SQLite database file named sample.db. It runs a query to get all data from the products table. Then it prints each row's content.

LangChain

from langchain.document_loaders import SQLDatabaseLoader

# Connect to a sample SQLite database and load all rows from 'products' table
loader = SQLDatabaseLoader(
    database_uri="sqlite:///sample.db",
    sql_query="SELECT * FROM products"
)
documents = loader.load()

for doc in documents:
    print(doc.page_content)

Important Notes

Make sure your database URI is correct and accessible.

The SQL query must be valid for your database type.

Loading large data sets may take time; consider filtering with SQL.

Summary

Loading from databases lets you use stored data in your programs.

Use SQLDatabaseLoader with a database URI and SQL query.

Always check your query and connection details before loading.