Integrating MySQL with ClickHouse

This page covers using the MySQL table engine, for reading from a MySQL table.

Connecting ClickHouse to MySQL using the MySQL Table Engine

The MySQL table engine allows you to connect ClickHouse to MySQL. SELECT and INSERT statements can be made in either ClickHouse or in the MySQL table. This article illustrates the basic methods of how to use the MySQL table engine.

Configure MySQL

Create a database in MySQL:

CREATE DATABASE db1;

Create a table:

CREATE TABLE db1.table1 (
  id INT,
  column1 VARCHAR(255)
);

Insert sample rows:

INSERT INTO db1.table1
  (id, column1)
VALUES
  (1, 'abc'),
  (2, 'def'),
  (3, 'ghi');

Create a user to connect from ClickHouse:

CREATE USER 'mysql_clickhouse'@'%' IDENTIFIED BY 'Password123!';

Grant privileges as needed. (For demonstration purposes, the mysql_clickhouse user is granted admin privileges.)

GRANT ALL PRIVILEGES ON *.* TO 'mysql_clickhouse'@'%';

Define a Table in ClickHouse

Now let’s create a ClickHouse table that uses the MySQL table engine:

CREATE TABLE mysql_table1 (
  id UInt64,
  column1 String
)
ENGINE = MySQL('mysql-host.domain.com','db1','table1','mysql_clickhouse','Password123!')

The minimum parameters are:

parameter	Description	example
host	hostname or IP	mysql-host.domain.com
database	mysql database name	db1
table	mysql table name	table1
user	username to connect to mysql	mysql_clickhouse
password	password to connect to mysql	Password123!

Test the Integration

In MySQL, insert a sample row:

INSERT INTO db1.table1
  (id, column1)
VALUES
  (4, 'jkl');

Notice the existing rows from the MySQL table are in the ClickHouse table, along with the new row you just added:

SELECT
    id,
    column1
FROM mysql_table1

You should see 4 rows:

Query id: 6d590083-841e-4e95-8715-ef37d3e95197

┌─id─┬─column1─┐
│  1 │ abc     │
│  2 │ def     │
│  3 │ ghi     │
│  4 │ jkl     │
└────┴─────────┘

4 rows in set. Elapsed: 0.044 sec.

Let’s add a row to the ClickHouse table:

INSERT INTO mysql_table1
  (id, column1)
VALUES
  (5,'mno')

Notice the new row appears in MySQL:

mysql> select id,column1 from db1.table1;

You should see the new row:

+------+---------+
| id   | column1 |
+------+---------+
|    1 | abc     |
|    2 | def     |
|    3 | ghi     |
|    4 | jkl     |
|    5 | mno     |
+------+---------+
5 rows in set (0.01 sec)

Summary

The MySQL table engine allows you to connect ClickHouse to MySQL to exchange data back and forth. For more details, be sure to check out the documentation page for the MySQL table engine.