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112 lines
3.7 KiB
Markdown
112 lines
3.7 KiB
Markdown
---
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slug: /zh/sql-reference/table-functions/mysql
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---
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# mysql {#mysql}
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允许对存储在远程MySQL服务器上的数据执行`SELECT`和`INSERT`查询。
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**语法**
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``` sql
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mysql('host:port', 'database', 'table', 'user', 'password'[, replace_query, 'on_duplicate_clause']);
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```
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**参数**
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- `host:port` — MySQL服务器地址.
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- `database` — 远程数据库名称.
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- `table` — 远程表名称.
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- `user` — MySQL用户.
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- `password` — 用户密码.
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- `replace_query` — 将INSERT INTO` 查询转换为 `REPLACE INTO`的标志。如果 `replace_query=1`，查询被替换。
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- `on_duplicate_clause` — 添加 `ON DUPLICATE KEY on_duplicate_clause` 表达式到 `INSERT` 查询。明确规定只能使用 `replace_query = 0` ，如果你同时设置replace_query = 1`和`on_duplicate_clause`，ClickHouse将产生异常。
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示例：`INSERT INTO t (c1,c2) VALUES ('a', 2) ON DUPLICATE KEY UPDATE c2 = c2 + 1`
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`on_duplicate_clause`这里是`UPDATE c2 = c2 + 1`。请查阅MySQL文档，来找到可以和`ON DUPLICATE KEY`一起使用的 `on_duplicate_clause`子句。
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简单的 `WHERE` 子句如 `=, !=, >, >=, <, <=` 将即时在MySQL服务器上执行。其余的条件和 `LIMIT` 只有在对MySQL的查询完成后，才会在ClickHouse中执行采样约束。
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支持使用`|`并列进行多副本查询，示例如下：
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```sql
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SELECT name FROM mysql(`mysql{1|2|3}:3306`, 'mysql_database', 'mysql_table', 'user', 'password');
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```
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或
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```sql
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SELECT name FROM mysql(`mysql1:3306|mysql2:3306|mysql3:3306`, 'mysql_database', 'mysql_table', 'user', 'password');
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```
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**返回值**
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与原始MySQL表具有相同列的表对象。
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:::note
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在`INSERT`查询中为了区分`mysql(...)`与带有列名列表的表名的表函数，你必须使用关键字`FUNCTION`或`TABLE FUNCTION`。查看如下示例。
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:::
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## 用法示例 {#usage-example}
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MySQL中的表:
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``` text
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mysql> CREATE TABLE `test`.`test` (
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-> `int_id` INT NOT NULL AUTO_INCREMENT,
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-> `int_nullable` INT NULL DEFAULT NULL,
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-> `float` FLOAT NOT NULL,
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-> `float_nullable` FLOAT NULL DEFAULT NULL,
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-> PRIMARY KEY (`int_id`));
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Query OK, 0 rows affected (0,09 sec)
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mysql> insert into test (`int_id`, `float`) VALUES (1,2);
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Query OK, 1 row affected (0,00 sec)
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mysql> select * from test;
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+------+----------+-----+----------+
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| int_id | int_nullable | float | float_nullable |
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+------+----------+-----+----------+
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| 1 | NULL | 2 | NULL |
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+------+----------+-----+----------+
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1 row in set (0,00 sec)
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```
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从ClickHouse中查询数据:
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``` sql
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SELECT * FROM mysql('localhost:3306', 'test', 'test', 'bayonet', '123')
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```
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``` text
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┌─int_id─┬─int_nullable─┬─float─┬─float_nullable─┐
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│ 1 │ ᴺᵁᴸᴸ │ 2 │ ᴺᵁᴸᴸ │
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└────────┴──────────────┴───────┴────────────────┘
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```
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替换和插入：
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```sql
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INSERT INTO FUNCTION mysql('localhost:3306', 'test', 'test', 'bayonet', '123', 1) (int_id, float) VALUES (1, 3);
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INSERT INTO TABLE FUNCTION mysql('localhost:3306', 'test', 'test', 'bayonet', '123', 0, 'UPDATE int_id = int_id + 1') (int_id, float) VALUES (1, 4);
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SELECT * FROM mysql('localhost:3306', 'test', 'test', 'bayonet', '123');
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```
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```text
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┌─int_id─┬─float─┐
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│ 1 │ 3 │
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│ 2 │ 4 │
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└────────┴───────┘
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```
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## 另请参阅 {#see-also}
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- [该 ‘MySQL’ 表引擎](../../engines/table-engines/integrations/mysql.md)
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- [使用MySQL作为外部字典的来源](../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-sources.md#dicts-external_dicts_dict_sources-mysql)
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