MCP SQL Server

A Model Context Protocol (MCP) server for querying PostgreSQL and MySQL databases.

Features

• Connect to PostgreSQL and MySQL databases
• Execute SQL queries
• List database tables
• Describe table schemas
• Parameterized query support
• Connection pooling for better performance

Installation

1. Install dependencies:

npm install

Usage

Running the Server

The server runs on stdio and communicates via the MCP protocol:

npm start

Available Tools

1. connect_database

Connect to a PostgreSQL or MySQL database. Parameters can be provided directly, loaded from environment variables, or a combination of both. If environment variables are set, the server will auto-connect on startup.

Parameters (all optional if using environment variables):

• type (string, optional): Database type - "postgresql" or "mysql"
• host (string, optional): Database host
• port (number, optional): Database port
• database (string, optional): Database name
• user (string, optional): Database user
• password (string, optional): Database password
• ssl (boolean, optional): Use SSL connection (default: false)

Examples:

Using parameters:

{
  "type": "postgresql",
  "host": "localhost",
  "port": 5432,
  "database": "mydb",
  "user": "postgres",
  "password": "password"
}

Using environment variables (call without parameters):

{}

Mixing parameters with environment variables:

{
  "type": "postgresql",
  "host": "custom-host"
}

2. execute_query

Execute a SQL query on the connected database.

Parameters:

• query (string, required): SQL query to execute
• params (array, optional): Query parameters for parameterized queries

Example:

{
  "query": "SELECT * FROM users WHERE id = $1",
  "params": [123]
}

3. list_tables

List all tables in the connected database.

Parameters: None

4. describe_table

Get schema information for a specific table.

Parameters:

• tableName (string, required): Name of the table to describe

Example:

{
  "tableName": "users"
}

5. disconnect_database

Disconnect from the current database.

Parameters: None

Configuration

Environment Variables

You can configure database connection using environment variables. Create a .env file in the project root or set environment variables:

Option 1: Generic Environment Variables (works for both PostgreSQL and MySQL)

DB_TYPE=postgresql          # or "mysql"
DB_HOST=localhost
DB_PORT=5432
DB_DATABASE=mydb
DB_USER=postgres
DB_PASSWORD=password
DB_SSL=false               # optional, set to "true" for SSL

Option 2: PostgreSQL-Specific Environment Variables

POSTGRES_HOST=localhost
POSTGRES_PORT=5432
POSTGRES_DATABASE=mydb
POSTGRES_USER=postgres
POSTGRES_PASSWORD=password
POSTGRES_SSL=false         # optional

Option 3: MySQL-Specific Environment Variables

MYSQL_HOST=localhost
MYSQL_PORT=3306
MYSQL_DATABASE=mydb
MYSQL_USER=root
MYSQL_PASSWORD=password
MYSQL_SSL=false            # optional

Note: If environment variables are set, the server will automatically connect on startup. You can also call connect_database without parameters to use environment variables, or provide partial parameters that will be merged with environment variables.

MCP Client Configuration

Add this to your MCP client configuration (e.g., in Cursor or other MCP-compatible tools):

{
  "mcpServers": {
    "sql": {
      "command": "node",
      "args": ["/Users/tranchihuu/Desktop/mcp-sql/index.js"],
      "cwd": "/Users/tranchihuu/Desktop/mcp-sql",
      "env": {
        "DB_TYPE": "postgresql",
        "DB_HOST": "localhost",
        "DB_PORT": "5432",
        "DB_DATABASE": "mydb",
        "DB_USER": "postgres",
        "DB_PASSWORD": "password"
      }
    }
  }
}

Important: Always include "cwd" when using the node command directly, so Node can find the node_modules directory.

Or if using npm script:

{
  "mcpServers": {
    "sql": {
      "command": "npm",
      "args": ["start"],
      "cwd": "/Users/tranchihuu/Desktop/mcp-sql",
      "env": {
        "DB_TYPE": "postgresql",
        "DB_HOST": "localhost",
        "DB_PORT": "5432",
        "DB_DATABASE": "mydb",
        "DB_USER": "postgres",
        "DB_PASSWORD": "password"
      }
    }
  }
}

Development

The project uses plain JavaScript (ES modules), so no build step is required. Just edit index.js and run npm start.

Security Notes

• Never commit database credentials to version control
• Use environment variables or secure credential management
• The server supports SSL connections for secure database access
• Always validate and sanitize SQL queries in production environments

Requirements

• Node.js 18+
• PostgreSQL or MySQL database access

License

MIT