SQL Query MCP Server

A Model Context Protocol (MCP) server that provides safe, read-only access to SQL databases through SELECT queries. This server runs in a Docker container and can be integrated with VS Code and other MCP-compatible clients.

Features

• Security First: Only SELECT queries are allowed - all data-modifying operations are blocked
• Multi-Database Support: Works with SQL Server (MSSQL), MySQL, and PostgreSQL
• Containerized: Runs in Docker for isolation and easy deployment
• Schema Discovery: Built-in tools to explore database structure and relationships
• Foreign Key Detection: Automatically discover table relationships for complex queries
• VS Code Integration: Ready to use as a tool in VS Code with GitHub Copilot

Available Tools

1. execute_select_query

Execute a SELECT query on the database.

Parameters:

• query (string): The SELECT SQL query to execute

Example:

SELECT * FROM Users WHERE age > 18

2. get_database_schema

Get the complete database schema including all tables and columns with their data types.

3. list_tables

List all tables in the database.

4. get_table_relationships

Get foreign key relationships between tables. Shows which columns reference other tables, essential for understanding how to join tables in complex queries.

Returns:

• constraint_name: Name of the foreign key constraint
• table_name: The table that contains the foreign key
• column_name: The column that is a foreign key
• referenced_table: The table being referenced
• referenced_column: The column being referenced

Example use case:

Q: "Check the relationship between Orders, Customers and Products. 
    Which foreign keys should I use to create a complex query?"

A: The tool returns:
   - Orders.CustomerID → Customers.CustomerID
   - Orders.ProductID → Products.ProductID

Setup

Prerequisites

• Docker and Docker Compose
• Node.js 20+ (for local development)
• Access to a SQL database (MSSQL, MySQL, or PostgreSQL)

Configuration

1. Copy the environment example file:

   cp .env.example .env
   

2. Edit .env with your database credentials:

   DB_TYPE=mssql              # Options: mssql, mysql, postgres
   DB_HOST=host.docker.internal  # For Docker to access host machine
   DB_PORT=1433
   DB_USER=your_user
   DB_PASSWORD=your_password
   DB_NAME=your_database
   DB_ENCRYPT=false           # Set to true for Azure SQL
   

Building and Running

Option 1: Using Docker Compose (Recommended)

docker-compose up --build

Option 2: Using Docker directly

# Build the image
docker build -t mcp-sql-query-server .

# Run the container
docker run -i \
  -e DB_TYPE=mssql \
  -e DB_HOST=host.docker.internal \
  -e DB_PORT=1433 \
  -e DB_USER=sa \
  -e DB_PASSWORD=YourPassword \
  -e DB_NAME=master \
  mcp-sql-query-server

Option 3: Local Development (without Docker)

# Install dependencies
npm install

# Build TypeScript
npm run build

# Set environment variables and run
export DB_TYPE=mssql
export DB_HOST=localhost
export DB_PORT=1433
export DB_USER=sa
export DB_PASSWORD=YourPassword
export DB_NAME=master

npm start

VS Code Integration

To use this MCP server with VS Code and GitHub Copilot:

1. Configure MCP in VS Code

Create or edit your MCP settings file. The location depends on your OS:

• Windows: %APPDATA%\Code\User\globalStorage\github.copilot-chat\mcp.json
• macOS: ~/Library/Application Support/Code/User/globalStorage/github.copilot-chat/mcp.json
• Linux: ~/.config/Code/User/globalStorage/github.copilot-chat/mcp.json

2. Add the Server Configuration

For Docker Container:

{
  "mcpServers": {
    "sql-query": {
      "command": "docker",
      "args": [
        "run",
        "-i",
        "--rm",
        "-e", "DB_TYPE=mssql",
        "-e", "DB_HOST=host.docker.internal",
        "-e", "DB_PORT=1433",
        "-e", "DB_USER=sa",
        "-e", "DB_PASSWORD=YourPassword",
        "-e", "DB_NAME=YourDatabase",
        "mcp-sql-query-server"
      ]
    }
  }
}

For Local Node.js:

{
  "mcpServers": {
    "sql-query": {
      "command": "node",
      "args": ["c:/Users/mzulber/personal-projects/mcp-servers/sql-server-query/dist/index.js"],
      "env": {
        "DB_TYPE": "mssql",
        "DB_HOST": "localhost",
        "DB_PORT": "1433",
        "DB_USER": "sa",
        "DB_PASSWORD": "YourPassword",
        "DB_NAME": "YourDatabase"
      }
    }
  }
}

3. Restart VS Code

After adding the configuration, restart VS Code for the changes to take effect.

4. Using in VS Code

Once configured, you can use the SQL query tools in GitHub Copilot Chat:

Example prompts:

• "List all tables in the database"
• "Show me the schema for the Users table"
• "Query the top 10 orders from last month"
• "What columns are in the Products table?"
• "Check the relationship between Orders, Customers and Products. Which foreign keys should I use to create a complex query?"
• "Show me how the tables are related in this database"

The Copilot will use the MCP server to execute your queries safely.

Security Features

1. Query Validation: Only SELECT statements are allowed
2. Keyword Blocking: Blocks queries containing INSERT, UPDATE, DELETE, DROP, CREATE, ALTER, TRUNCATE, EXEC, etc.
3. No Dynamic SQL: Prevents execution of stored procedures or dynamic SQL
4. Read-Only Access: Configure your database user with read-only permissions for additional security

Database-Specific Notes

SQL Server (MSSQL)

• Default port: 1433
• Supports both Windows and SQL Server authentication
• For Azure SQL, set DB_ENCRYPT=true

MySQL

• Default port: 3306
• Ensure user has SELECT privileges on the target database

PostgreSQL

• Default port: 5432
• Connects to specific database specified in DB_NAME

Troubleshooting

Container can't connect to database on host machine

Use host.docker.internal instead of localhost for DB_HOST when running in Docker.

Connection timeout

• Check firewall settings
• Verify database is listening on the specified port
• Ensure database allows connections from Docker network

VS Code doesn't see the tools

1. Check that the mcp.json file is in the correct location
2. Restart VS Code
3. Check VS Code Developer Tools Console for errors (Help > Toggle Developer Tools)

Development

Watch mode for development:

npm run watch

Build only:

npm run build

License

MIT