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150 lines
4.3 KiB
Markdown
150 lines
4.3 KiB
Markdown
---
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slug: /zh/engines/database-engines/mysql
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sidebar_position: 30
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sidebar_label: MySQL
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---
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# MySQL {#mysql}
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MySQL引擎用于将远程的MySQL服务器中的表映射到ClickHouse中，并允许您对表进行`INSERT`和`SELECT`查询，以方便您在ClickHouse与MySQL之间进行数据交换
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`MySQL`数据库引擎会将对其的查询转换为MySQL语法并发送到MySQL服务器中，因此您可以执行诸如`SHOW TABLES`或`SHOW CREATE TABLE`之类的操作。
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但您无法对其执行以下操作：
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- `RENAME`
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- `CREATE TABLE`
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- `ALTER`
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## 创建数据库 {#creating-a-database}
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``` sql
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CREATE DATABASE [IF NOT EXISTS] db_name [ON CLUSTER cluster]
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ENGINE = MySQL('host:port', ['database' | database], 'user', 'password')
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```
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**引擎参数**
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- `host:port` — MySQL服务地址
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- `database` — MySQL数据库名称
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- `user` — MySQL用户名
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- `password` — MySQL用户密码
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## 支持的数据类型 {#data_types-support}
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| MySQL | ClickHouse |
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|----------------------------------|--------------------------------------------------------------|
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| UNSIGNED TINYINT | [UInt8](../../sql-reference/data-types/int-uint.md) |
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| TINYINT | [Int8](../../sql-reference/data-types/int-uint.md) |
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| UNSIGNED SMALLINT | [UInt16](../../sql-reference/data-types/int-uint.md) |
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| SMALLINT | [Int16](../../sql-reference/data-types/int-uint.md) |
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| UNSIGNED INT, UNSIGNED MEDIUMINT | [UInt32](../../sql-reference/data-types/int-uint.md) |
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| INT, MEDIUMINT | [Int32](../../sql-reference/data-types/int-uint.md) |
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| UNSIGNED BIGINT | [UInt64](../../sql-reference/data-types/int-uint.md) |
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| BIGINT | [Int64](../../sql-reference/data-types/int-uint.md) |
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| FLOAT | [Float32](../../sql-reference/data-types/float.md) |
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| DOUBLE | [Float64](../../sql-reference/data-types/float.md) |
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| DATE | [Date](../../sql-reference/data-types/date.md) |
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| DATETIME, TIMESTAMP | [DateTime](../../sql-reference/data-types/datetime.md) |
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| BINARY | [FixedString](../../sql-reference/data-types/fixedstring.md) |
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其他的MySQL数据类型将全部都转换为[String](../../sql-reference/data-types/string.md).
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[Nullable](../../sql-reference/data-types/nullable.md)已经支持
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## 全局变量支持 {#global-variables-support}
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为了更好地兼容，您可以在SQL样式中设置全局变量，如`@@identifier`.
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支持这些变量：
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- `version`
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- `max_allowed_packet`
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!!! warning "警告"
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到目前为止，这些变量是存根，并且不对应任何内容。
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示例:
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``` sql
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SELECT @@version;
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```
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## 使用示例 {#examples-of-use}
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MySQL操作:
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``` text
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mysql> USE test;
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Database changed
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mysql> CREATE TABLE `mysql_table` (
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-> `int_id` INT NOT NULL AUTO_INCREMENT,
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-> `float` FLOAT NOT 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 mysql_table (`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 mysql_table;
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+------+-----+
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| int_id | value |
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+------+-----+
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| 1 | 2 |
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+------+-----+
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1 row in set (0,00 sec)
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```
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ClickHouse中的数据库，与MySQL服务器交换数据:
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``` sql
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CREATE DATABASE mysql_db ENGINE = MySQL('localhost:3306', 'test', 'my_user', 'user_password')
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```
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``` sql
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SHOW DATABASES
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```
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``` text
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┌─name─────┐
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│ default │
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│ mysql_db │
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│ system │
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└──────────┘
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```
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``` sql
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SHOW TABLES FROM mysql_db
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```
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``` text
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┌─name─────────┐
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│ mysql_table │
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└──────────────┘
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```
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``` sql
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SELECT * FROM mysql_db.mysql_table
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```
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``` text
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┌─int_id─┬─value─┐
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│ 1 │ 2 │
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└────────┴───────┘
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```
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``` sql
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INSERT INTO mysql_db.mysql_table VALUES (3,4)
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```
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``` sql
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SELECT * FROM mysql_db.mysql_table
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```
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``` text
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┌─int_id─┬─value─┐
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│ 1 │ 2 │
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│ 3 │ 4 │
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└────────┴───────┘
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```
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