Loading from databases in LangChain - Mini Project: Build & Apply

Loading Data from a Database with LangChain

📖 Scenario: You are building a simple app that fetches data from a database to use with LangChain. This helps you get information ready for your language model to understand.

🎯 Goal: Learn how to connect to a database, configure a query, load data using LangChain's database loader, and prepare it for further processing.

📋 What You'll Learn

Create a database connection string variable

Set up a SQL query string variable

Use LangChain's SQLDatabase and SQLDatabaseChain to load data

Complete the setup to run the database query and load results

💡 Why This Matters

🌍 Real World

Loading data from databases is common when building apps that use language models to understand or analyze real data stored in databases.

💼 Career

Many jobs require connecting language models to databases to automate data retrieval, reporting, or building intelligent assistants.

1

Create the database connection string

Create a variable called connection_string and set it to the exact value "sqlite:///example.db".

LangChain

# Your code here

Need a hint?

This string tells LangChain where your database is located. Use the exact text including quotes.

2

Set up the SQL query string

Create a variable called query and set it to the exact SQL query string "SELECT * FROM users".

LangChain

connection_string = "sqlite:///example.db"
# Your code here

Need a hint?

This query will select all data from the users table in your database.

3

Load data using LangChain's SQLDatabase

Import SQLDatabase from langchain_sql_database and create a variable called db by calling SQLDatabase.from_uri(connection_string).

LangChain

connection_string = "sqlite:///example.db"
query = "SELECT * FROM users"
# Your code here

Need a hint?

Use the exact import and method call to create the database object.

4

Create the SQLDatabaseChain and run the query

Import SQLDatabaseChain from langchain_chains. Then create a variable called db_chain by calling SQLDatabaseChain(database=db, query=query).

LangChain

from langchain_sql_database import SQLDatabase

connection_string = "sqlite:///example.db"
query = "SELECT * FROM users"
db = SQLDatabase.from_uri(connection_string)
# Your code here

Need a hint?

This sets up the chain that will run your SQL query using LangChain.