# 使用其他数据库引擎中的数据类型

为了便于使用为其他供应商的 SQL 实现编写的代码，MySQL 映射了数据类型，如下表所示。这些映射使得从其他数据库系统导入表定义到 MySQL 变得更加简单。

| Other Vendor Type    | MySQL Type |
| -------------------- | ---------- |
| BOOL                 | TINYINT    |
| BOOLEAN              | TINYINT    |
| CHARACTER VARYING(M) | VARCHAR(M) |
| FIXED                | DECIMAL    |
| FLOAT4               | FLOAT      |
| FLOAT8               | BOUBLE     |
| INT1                 | TINYINT    |
| INT2                 | SMALLINT   |
| INT3                 | MEDIUMINT  |
| INT4                 | INT        |
| INT8                 | BIGINT     |
| LONG VARBINARY       | MEDIUMBLOB |
| LONG VARCHAR         | MEDIUMTEXT |
| LONG                 | MEDIUMTEXT |
| MIDDLEINT            | MEDIUMINT  |
| NUMERIC              | DECIMAL    |

数据类型映射在创建表时发生，此后原始类型就会失效。如果使用其他供应商的类型创建表，然后执行 DESCRIBE tbl\_name 语句，MySQL 会使用等效的 MySQL 类型报告表的结构。例如：

```bash
mysql> CREATE TABLE t (a BOOL, b FLOAT8, c LONG VARCHAR, d NUMERIC);
Query OK, 0 rows affected (0.00 sec)

mysql> DESCRIBE t;
+-------+---------------+------+-----+---------+-------+
| Field | Type          | Null | Key | Default | Extra |
+-------+---------------+------+-----+---------+-------+
| a     | tinyint(1)    | YES  |     | NULL    |       |
| b     | double        | YES  |     | NULL    |       |
| c     | mediumtext    | YES  |     | NULL    |       |
| d     | decimal(10,0) | YES  |     | NULL    |       |
+-------+---------------+------+-----+---------+-------+
4 rows in set (0.01 sec)
```


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