ClickHouse/docs/en/sql-reference/table-functions/mysql.md

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slug: /en/sql-reference/table-functions/mysql
sidebar_position: 137
sidebar_label: mysql
---

# 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'[, replace_query, 'on_duplicate_clause'])
```

**Arguments**

- `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`.

- `on_duplicate_clause` — The `ON DUPLICATE KEY on_duplicate_clause` expression that is added to the `INSERT` query. Can be specified only with `replace_query = 0` (if you simultaneously pass `replace_query = 1` and `on_duplicate_clause`, ClickHouse generates an exception).

    Example: `INSERT INTO t (c1,c2) VALUES ('a', 2) ON DUPLICATE KEY UPDATE c2 = c2 + 1;`

    `on_duplicate_clause` here is `UPDATE c2 = c2 + 1`. See the MySQL documentation to find which `on_duplicate_clause` you can use with the `ON DUPLICATE KEY` clause.

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`, 'mysql_database', 'mysql_table', 'user', 'password');
```

or

```sql
SELECT name FROM mysql(`mysql1:3306|mysql2:3306|mysql3:3306`, 'mysql_database', 'mysql_table', '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` (
    ->   `int_id` INT NOT NULL AUTO_INCREMENT,
    ->   `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');
```

``` text
┌─int_id─┬─float─┐
│      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 int_id = int_id + 1') (int_id, float) VALUES (1, 4);
SELECT * FROM mysql('localhost:3306', 'test', 'test', 'bayonet', '123');
```

``` text
┌─int_id─┬─float─┐
│      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**

- [The ‘MySQL’ table engine](../../engines/table-engines/integrations/mysql.md)
- [Using MySQL as a dictionary source](../../sql-reference/dictionaries/index.md#dictionary-sources#dicts-external_dicts_dict_sources-mysql)