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Using MySQL2 with TypeScript

Installation

npm install --save mysql2
npm install --save-dev @types/node

The @types/node ensure the proper interaction between TypeScript and the Node.js modules used by MySQL2 (net, events, stream, tls, etc.).

Requires TypeScript >=4.5.2.

Usage

You can import MySQL2 in two ways:

  • By setting the esModuleInterop option to true in tsconfig.json
import mysql from 'mysql2';
import mysql from 'mysql2/promise';
  • By setting the esModuleInterop option to false in tsconfig.json
import * as mysql from 'mysql2';
import * as mysql from 'mysql2/promise';

Connection

import mysql, { ConnectionOptions } from 'mysql2';

const access: ConnectionOptions = {
  user: 'test',
  database: 'test',
};

const conn = mysql.createConnection(access);

Pool Connection

import mysql, { PoolOptions } from 'mysql2';

const access: PoolOptions = {
  user: 'test',
  database: 'test',
};

const conn = mysql.createPool(access);

Query and Execute

A simple query

conn.query('SELECT 1 + 1 AS `test`;', (_err, rows) => {
  /**
   * @rows: [ { test: 2 } ]
   */
});

conn.execute('SELECT 1 + 1 AS `test`;', (_err, rows) => {
  /**
   * @rows: [ { test: 2 } ]
   */
});

The rows output will be these possible types:

  • RowDataPacket[]
  • RowDataPacket[][]
  • ResultSetHeader
  • ResultSetHeader[]
  • ProcedureCallPacket

In this example, you need to manually check the output types

Type Specification

RowDataPacket[]

An array with the returned rows, for example:

import mysql, { RowDataPacket } from 'mysql2';

const conn = mysql.createConnection({
  user: 'test',
  database: 'test',
});

// SELECT
conn.query<RowDataPacket[]>('SELECT 1 + 1 AS `test`;', (_err, rows) => {
  console.log(rows);
  /**
   * @rows: [ { test: 2 } ]
   */
});

// SHOW
conn.query<RowDataPacket[]>('SHOW TABLES FROM `test`;', (_err, rows) => {
  console.log(rows);
  /**
   * @rows: [ { Tables_in_test: 'test' } ]
   */
});

Using rowsAsArray option as true:

import mysql, { RowDataPacket } from 'mysql2';

const conn = mysql.createConnection({
  user: 'test',
  database: 'test',
  rowsAsArray: true,
});

// SELECT
conn.query<RowDataPacket[]>('SELECT 1 + 1 AS test, 2 + 2 AS test;', (_err, rows) => {
  console.log(rows);
  /**
  * @rows: [ [ 2, 4 ] ]
  */
});

// SHOW
conn.query<RowDataPacket[]>('SHOW TABLES FROM `test`;', (_err, rows) => {
  console.log(rows);
  /**
  * @rows: [ [ 'test' ] ]
  */
});

RowDataPacket[][]

Using multipleStatementsoption as true with multiple queries:

import mysql, { RowDataPacket } from 'mysql2';

const conn = mysql.createConnection({
  user: 'test',
  database: 'test',
  multipleStatements: true,
});

const sql = `
  SELECT 1 + 1 AS test;
  SELECT 2 + 2 AS test;
`;

conn.query<RowDataPacket[][]>(sql, (_err, rows) => {
  console.log(rows);
  /**
  * @rows: [ [ { test: 2 } ], [ { test: 4 } ] ]
  */
});

ResultSetHeader

For INSERT, UPDATE, DELETE, TRUNCATE, etc.:

import mysql, { ResultSetHeader } from 'mysql2';

const conn = mysql.createConnection({
  user: 'test',
  database: 'test',
});

const sql = `
  SET @1 = 1;
`;

conn.query<ResultSetHeader>(sql, (_err, result) => {
  console.log(result);
  /**
   * @result: ResultSetHeader {
      fieldCount: 0,
      affectedRows: 0,
      insertId: 0,
      info: '',
      serverStatus: 2,
      warningStatus: 0,
      changedRows: 0
    }
   */
});

ResultSetHeader[]

For multiples INSERT, UPDATE, DELETE, TRUNCATE, etc. when using multipleStatements as true:

import mysql, { ResultSetHeader } from 'mysql2';

const conn = mysql.createConnection({
  user: 'test',
  database: 'test',
  multipleStatements: true,
});

const sql = `
  SET @1 = 1;
  SET @2 = 2;
`;

conn.query<ResultSetHeader[]>(sql, (_err, results) => {
  console.log(results);
  /**
   * @results: [
      ResultSetHeader {
        fieldCount: 0,
        affectedRows: 0,
        insertId: 0,
        info: '',
        serverStatus: 10,
        warningStatus: 0,
        changedRows: 0
      },
      ResultSetHeader {
        fieldCount: 0,
        affectedRows: 0,
        insertId: 0,
        info: '',
        serverStatus: 2,
        warningStatus: 0,
        changedRows: 0
      }
    ]
   */
});

ProcedureCallPacket

By performing a Call Procedure using INSERT, UPDATE, etc., the return will be a ProcedureCallPacket<ResultSetHeader> (even if you perform multiples queries and set multipleStatements to true):

import mysql, { ProcedureCallPacket, ResultSetHeader } from 'mysql2';

const conn = mysql.createConnection({
  user: 'test',
  database: 'test',
});

/** ResultSetHeader */
conn.query('DROP PROCEDURE IF EXISTS myProcedure');

/** ResultSetHeader */
conn.query(`
    CREATE PROCEDURE myProcedure()
    BEGIN
      SET @1 = 1;
      SET @2 = 2;
    END
  `);

/** ProcedureCallPacket */
const sql = 'CALL myProcedure()';

conn.query<ProcedureCallPacket<ResultSetHeader>>(sql, (_err, result) => {
  console.log(result);
  /**
   * @result: ResultSetHeader {
      fieldCount: 0,
      affectedRows: 0,
      insertId: 0,
      info: '',
      serverStatus: 2,
      warningStatus: 0,
      changedRows: 0
    }
   */
});

For CREATE PROCEDURE and DROP PROCEDURE, these returns will be the default ResultSetHeader.

By using SELECT and SHOW queries in a Procedure Call, it groups the results as:

/** ProcedureCallPacket<RowDataPacket[]> */
[RowDataPacket[], ResultSetHeader]

For ProcedureCallPacket<RowDataPacket[]>, please see the following examples.

Examples

You can also check some code examples using MySQL2 and TypeScript to understand advanced concepts: