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125 lines
3.2 KiB
Markdown
125 lines
3.2 KiB
Markdown
# 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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- `ATTACH`/`DETACH`
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- `DROP`
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- `RENAME`
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- `CREATE TABLE`
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- `ALTER`
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## 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', '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
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MySQL | ClickHouse
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------|------------
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UNSIGNED TINYINT | [UInt8](../data_types/int_uint.md)
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TINYINT | [Int8](../data_types/int_uint.md)
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UNSIGNED SMALLINT | [UInt16](../data_types/int_uint.md)
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SMALLINT | [Int16](../data_types/int_uint.md)
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UNSIGNED INT, UNSIGNED MEDIUMINT | [UInt32](../data_types/int_uint.md)
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INT, MEDIUMINT | [Int32](../data_types/int_uint.md)
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UNSIGNED BIGINT | [UInt64](../data_types/int_uint.md)
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BIGINT | [Int64](../data_types/int_uint.md)
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FLOAT | [Float32](../data_types/float.md)
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DOUBLE | [Float64](../data_types/float.md)
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DATE | [Date](../data_types/date.md)
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DATETIME, TIMESTAMP | [DateTime](../data_types/datetime.md)
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BINARY | [FixedString](../data_types/fixedstring.md)
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其他的MySQL数据类型将全部都转换为[String](../data_types/string.md)。
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同时以上的所有类型都支持[Nullable](../data_types/nullable.md)。
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## 使用示例
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在MySQL中创建表:
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```
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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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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.yandex/docs/en/database_engines/mysql/) <!--hide-->
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