mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-15 20:24:07 +00:00
d91c97d15d
* Replace underscores with hyphens * remove temporary code * fix style check * fix collapse
85 lines
3.0 KiB
Markdown
85 lines
3.0 KiB
Markdown
---
|
||
toc_priority: 42
|
||
toc_title: mysql
|
||
---
|
||
|
||
# mysql {#mysql}
|
||
|
||
Allows `SELECT` queries to be performed on data that is stored on a remote MySQL server.
|
||
|
||
``` sql
|
||
mysql('host:port', 'database', 'table', 'user', 'password'[, replace_query, 'on_duplicate_clause']);
|
||
```
|
||
|
||
**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`. If `replace_query=1`, the query is replaced.
|
||
|
||
- `on_duplicate_clause` — The `ON DUPLICATE KEY on_duplicate_clause` expression that is added to the `INSERT` query.
|
||
|
||
Example: `INSERT INTO t (c1,c2) VALUES ('a', 2) ON DUPLICATE KEY UPDATE c2 = c2 + 1`, where `on_duplicate_clause` is `UPDATE c2 = c2 + 1`. See the MySQL documentation to find which `on_duplicate_clause` you can use with the `ON DUPLICATE KEY` clause.
|
||
|
||
To specify `on_duplicate_clause` you need to pass `0` to the `replace_query` parameter. If you simultaneously pass `replace_query = 1` and `on_duplicate_clause`, ClickHouse generates an exception.
|
||
|
||
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.
|
||
|
||
**Returned Value**
|
||
|
||
A table object with the same columns as the original MySQL table.
|
||
|
||
## Usage Example {#usage-example}
|
||
|
||
Table in MySQL:
|
||
|
||
``` text
|
||
mysql> CREATE TABLE `test`.`test` (
|
||
-> `int_id` INT NOT NULL AUTO_INCREMENT,
|
||
-> `int_nullable` INT NULL DEFAULT NULL,
|
||
-> `float` FLOAT NOT NULL,
|
||
-> `float_nullable` FLOAT NULL DEFAULT NULL,
|
||
-> PRIMARY KEY (`int_id`));
|
||
Query OK, 0 rows affected (0,09 sec)
|
||
|
||
mysql> insert into test (`int_id`, `float`) VALUES (1,2);
|
||
Query OK, 1 row affected (0,00 sec)
|
||
|
||
mysql> select * from test;
|
||
+------+----------+-----+----------+
|
||
| int_id | int_nullable | float | float_nullable |
|
||
+------+----------+-----+----------+
|
||
| 1 | NULL | 2 | NULL |
|
||
+------+----------+-----+----------+
|
||
1 row in set (0,00 sec)
|
||
```
|
||
|
||
Selecting data from ClickHouse:
|
||
|
||
``` sql
|
||
SELECT * FROM mysql('localhost:3306', 'test', 'test', 'bayonet', '123')
|
||
```
|
||
|
||
``` text
|
||
┌─int_id─┬─int_nullable─┬─float─┬─float_nullable─┐
|
||
│ 1 │ ᴺᵁᴸᴸ │ 2 │ ᴺᵁᴸᴸ │
|
||
└────────┴──────────────┴───────┴────────────────┘
|
||
```
|
||
|
||
## See Also {#see-also}
|
||
|
||
- [The ‘MySQL’ table engine](../../engines/table-engines/integrations/mysql.md)
|
||
- [Using MySQL as a source of external dictionary](../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-sources.md#dicts-external_dicts_dict_sources-mysql)
|
||
|
||
[Original article](https://clickhouse.tech/docs/en/query_language/table_functions/mysql/) <!--hide-->
|