mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-27 18:12:02 +00:00
73 lines
2.9 KiB
Markdown
73 lines
2.9 KiB
Markdown
# mysql
|
|
|
|
Allows to perform `SELECT` queries on data that is stored on a remote MySQL server.
|
|
|
|
```
|
|
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 sets query substitution `INSERT INTO` 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 MySQL documentation to find which `on_duplicate_clause` you can use with `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.
|
|
|
|
At this time, simple `WHERE` clauses and elements of `AND` chain in `WHERE` clause such as `=, !=, >, >=, <, <=, LIKE, IN` with compatible functions are also pushed down for execution on the MySQL server.
|
|
|
|
The rest of the conditions and the `LIMIT` 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
|
|
|
|
Table in MySQL:
|
|
|
|
```
|
|
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)
|
|
```
|
|
|
|
Selection of the 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
|
|
|
|
- [The 'MySQL' table engine](../../operations/table_engines/mysql.md)
|
|
- [Using MySQL as a source of extenal dictionary](../dicts/external_dicts_dict_sources.md#dicts-external_dicts_dict_sources-mysql)
|
|
|
|
[Original article](https://clickhouse.yandex/docs/en/query_language/table_functions/mysql/) <!--hide-->
|