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127 lines
4.2 KiB
Markdown
127 lines
4.2 KiB
Markdown
# 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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## CREATE DATABASE {#create-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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**MySQL数据库引擎参数**
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- `host:port` — 链接的MySQL地址。
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- `database` — 链接的MySQL数据库。
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- `user` — 链接的MySQL用户。
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- `password` — 链接的MySQL用户密码。
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## 支持的类型对应 {#zhi-chi-de-lei-xing-dui-ying}
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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 | [日期](../../sql-reference/data-types/date.md) |
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| DATETIME, TIMESTAMP | [日期时间](../../sql-reference/data-types/datetime.md) |
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| BINARY | [固定字符串](../../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[字符串](../../sql-reference/data-types/string.md)。
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同时以上的所有类型都支持[可为空](../../sql-reference/data-types/nullable.md)。
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## 使用示例 {#shi-yong-shi-li}
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在MySQL中创建表:
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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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在ClickHouse中创建MySQL类型的数据库，同时与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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[来源文章](https://clickhouse.tech/docs/en/database_engines/mysql/) <!--hide-->
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