Project: ClickHouse (App Definition and Development / Database)
File: mysql.md

slug: /en/sql-reference/table-functions/mysql sidebar_position: 137 sidebar_label: mysql Allows `SELECT` and `INSERT` queries to be performed on data that is stored on a remote MySQL server. Syntax ``` sql mysql({host:port, database, table, user, password[, replacequery, onduplicateclause] | namedcollection[, option=value [,..]]}) ``` Parameters `host:port` MySQL server address. `database` Remote database name. `table` Remote table name. `user` MySQL user. `password` User password. `replace_query` Flag that converts `INSERT INTO` queries to `REPLACE INTO`. Possible values: `0` - The query is executed as `INSERT INTO`. `1` - The query is executed as `REPLACE INTO`. `onduplicateclause` The `ON DUPLICATE KEY onduplicateclause` expression that is added to the `INSERT` query. Can be specified only with `replacequery = 0` (if you simultaneously pass `replacequery = 1` and `onduplicateclause`, ClickHouse generates an exception). Example: `INSERT INTO t (c1,c2) VALUES ('a', 2) ON DUPLICATE KEY UPDATE c2 = c2 + 1;` `onduplicateclause` here is `UPDATE c2 = c2 + 1`. See the MySQL documentation to find which `onduplicateclause` you can use with the `ON DUPLICATE KEY` clause. Arguments also can be passed using . In this case `host` and `port` should be specified separately. This approach is recommended for production environment. Simple `WHERE` clauses such as `=, !=, >, >=, <, <=` are currently executed on the MySQL server. The rest of the conditions and the `LIMIT` sampling constraint are executed in ClickHouse only after the query to MySQL finishes. Supports multiple replicas that must be listed by `|`. For example: ```sql SELECT name FROM mysql(`mysql{1|2|3}:3306`, 'mysqldatabase', 'mysqltable', 'user', 'password'); ``` or ```sql SELECT name FROM mysql(`mysql1:3306|mysql2:3306|mysql3:3306`, 'mysqldatabase', 'mysqltable', 'user', 'password'); ``` Returned Value A table object with the same columns as the original MySQL table. :::note In the `INSERT` query to distinguish table function `mysql(...)` from table name with column names list, you must use keywords `FUNCTION` or `TABLE FUNCTION`. See examples below. ::: Examples Table in MySQL: ``` text mysql> CREATE TABLE `test`.`test` ( -> `intid` INT NOT NULL AUTOINCREMENT, -> `float` FLOAT NOT NULL, -> PRIMARY KEY (`int_id`)); mysql> INSERT INTO test (`int_id`, `float`) VALUES (1,2); mysql> SELECT * FROM test; +--+-+ | int_id | float | +--+-+ | 1 | 2 | +--+-+ ``` Selecting data from ClickHouse: ``` sql SELECT * FROM mysql('localhost:3306', 'test', 'test', 'bayonet', '123'); ``` Or using : ```sql CREATE NAMED COLLECTION creds AS host = 'localhost', port = 3306, database = 'test', user = 'bayonet', password = '123'; SELECT * FROM mysql(creds, table='test'); ``` ``` text int_idfloat 1 2 ``` Replacing and inserting: ```sql INSERT INTO FUNCTION mysql('localhost:3306', 'test', 'test', 'bayonet', '123', 1) (int_id, float) VALUES (1, 3); INSERT INTO TABLE FUNCTION mysql('localhost:3306', 'test', 'test', 'bayonet', '123', 0, 'UPDATE intid = intid + 1') (int_id, float) VALUES (1, 4); SELECT * FROM mysql('localhost:3306', 'test', 'test', 'bayonet', '123'); ``` ``` text int_idfloat 1 3 2 4 ``` Copying data from MySQL table into ClickHouse table: ```sql CREATE TABLE mysql_copy ( `id` UInt64, `datetime` DateTime('UTC'), `description` String, ) ENGINE = MergeTree ORDER BY (id,datetime); INSERT INTO mysql_copy SELECT * FROM mysql('host:port', 'database', 'table', 'user', 'password'); ``` Or if copying only an incremental batch from MySQL based on the max current id: ```sql INSERT INTO mysql_copy SELECT * FROM mysql('host:port', 'database', 'table', 'user', 'password') WHERE id > (SELECT max(id) from mysql_copy); ``` See Also