MySQL表排序规则不一样报错是什么问题导致的？

发布时间：2023-08-02 15:38:29 所属栏目：MySql教程来源：

导读：MySQL表排序规则不同报错是什么问题导致的？很多人都不太了解，今天小编为了让大家更加了解MySQL表排序规则，所以给大家总结了以下内容，一起往下看吧。

MySQL多表join时报错如下：[Err]1267 – Illegal mi

MySQL表排序规则不同报错是什么问题导致的？很多人都不太了解，今天小编为了让大家更加了解MySQL表排序规则，所以给大家总结了以下内容，一起往下看吧。

MySQL多表join时报错如下：[Err]1267 – Illegal mix of collations(utf8_general_ci,IMPLICIT) and (utf8_unicode_ci,IMPLICIT) for operation ‘=

就是说两个表的排序规则（COLLATION）不同，无法完成比较。COLLATION是用在排序，大小比较上，一个字符集有一个或多种COLLATION，并且以_ci（大小写不敏感）、_cs（大小写敏感）或_bin（二进制）结束。在做比较时，应该确保两个表的字符排序相同。一般建表的时候不指定，可以走默认的，全是默认的就没什么问题了。本文主要介绍了MySQL表排序规则不同错误问题分析，希望能帮助到大家。

下面来模拟一下各种场景，表结构如下（utf8默认排序规则为utf8_general_ci）：

mysql> show create table test.cs\G

*************************** 1. row ***************************

    Table: cs

Create Table: CREATE TABLE `cs` (

`id` int(11) DEFAULT NULL,

`name` varchar(10) DEFAULT NULL

) ENGINE=InnoDB DEFAULT CHARSET=utf8

1 row in set (0.01 sec)

查看表默认排序规则集

mysql> select TABLE_SCHEMA,TABLE_NAME,TABLE_COLLATION from information_schema.tables where table_name='cs';

+--------------+------------+-----------------+

| TABLE_SCHEMA | TABLE_NAME | TABLE_COLLATION |

+--------------+------------+-----------------+

| test     | cs     | utf8_general_ci |

+--------------+------------+-----------------+

1 row in set (0.00 sec)

查看列排序规则集

mysql> select TABLE_SCHEMA,TABLE_NAME,COLUMN_NAME,COLLATION_NAME from information_schema.COLUMNS where TABLE_NAME='cs';

+--------------+------------+-------------+-----------------+

| TABLE_SCHEMA | TABLE_NAME | COLUMN_NAME | COLLATION_NAME |

+--------------+------------+-------------+-----------------+

| test     | cs     | id     | NULL      |

| test     | cs     | name    | utf8_general_ci |

+--------------+------------+-------------+-----------------+

2 rows in set (0.00 sec)

从utf8升级为utf8mb4是不支持online ddl的，如下：

mysql> ALTER TABLE cs CONVERT TO CHARACTER SET utf8mb4,ALGORITHM=INPLACE,LOCK=NONE;

ERROR 1846 (0A000): ALGORITHM=INPLACE is not supported. Reason: Cannot change column type INPLACE. Try ALGORITHM=COPY.

从utf8.utf8_general_ci变更为utf8.utf8_unicode_ci是不支持online ddl的，如下：

mysql> ALTER TABLE cs CONVERT TO CHARACTER SET utf8 collate utf8_unicode_ci,ALGORITHM=INPLACE,LOCK=NONE;

ERROR 1846 (0A000): ALGORITHM=INPLACE is not supported. Reason: Cannot change column type INPLACE. Try ALGORITHM=COPY.

如果使用下面这种方式修改字符集，你会发现，只更改了表级的，没有更改列级的。

mysql> ALTER TABLE cs CHARACTER SET utf8 collate utf8_unicode_ci;

Query OK, 0 rows affected (0.01 sec)

Records: 0 Duplicates: 0 Warnings: 0

mysql> select TABLE_SCHEMA,TABLE_NAME,TABLE_COLLATION from information_schema.tables where table_name='cs';

+--------------+------------+-----------------+

| TABLE_SCHEMA | TABLE_NAME | TABLE_COLLATION |

+--------------+------------+-----------------+

| test     | cs     | utf8_unicode_ci |

+--------------+------------+-----------------+

1 row in set (0.00 sec)

mysql> select TABLE_SCHEMA,TABLE_NAME,COLUMN_NAME,COLLATION_NAME from information_schema.COLUMNS where TABLE_NAME='cs';

+--------------+------------+-------------+-----------------+

| TABLE_SCHEMA | TABLE_NAME | COLUMN_NAME | COLLATION_NAME |

+--------------+------------+-------------+-----------------+

| test     | cs     | id     | NULL      |

| test     | cs     | name    | utf8_general_ci |

+--------------+------------+-------------+-----------------+

2 rows in set (0.00 sec)

所以真正改字符集的时候别忘了加上CONVERT TO，如下：

mysql> ALTER TABLE cs CONVERT TO CHARACTER SET utf8 collate utf8_unicode_ci;

Query OK, 5 rows affected (0.06 sec)

Records: 5 Duplicates: 0 Warnings: 0

mysql> select TABLE_SCHEMA,TABLE_NAME,COLUMN_NAME,COLLATION_NAME from information_schema.COLUMNS where TABLE_NAME='cs';

+--------------+------------+-------------+-----------------+

| TABLE_SCHEMA | TABLE_NAME | COLUMN_NAME | COLLATION_NAME |

+--------------+------------+-------------+-----------------+

| test     | cs     | id     | NULL      |

| test     | cs     | name    | utf8_unicode_ci |

+--------------+------------+-------------+-----------------+

2 rows in set (0.00 sec)

要仅仅改变一个表的默认字符集，应使用此语句：

mysql> ALTER TABLE cs default CHARACTER SET utf8 collate utf8_general_ci,ALGORITHM=INPLACE,LOCK=NONE;

Query OK, 0 rows affected (0.00 sec)

Records: 0 Duplicates: 0 Warnings: 0

mysql> select TABLE_SCHEMA,TABLE_NAME,TABLE_COLLATION from information_schema.tables where table_name='cs';

+--------------+------------+-----------------+

| TABLE_SCHEMA | TABLE_NAME | TABLE_COLLATION |

+--------------+------------+-----------------+

| test     | cs     | utf8_general_ci |

+--------------+------------+-----------------+

1 row in set (0.00 sec)

mysql> select TABLE_SCHEMA,TABLE_NAME,COLUMN_NAME,COLLATION_NAME from information_schema.COLUMNS where TABLE_NAME='cs';

+--------------+------------+-------------+-----------------+

| TABLE_SCHEMA | TABLE_NAME | COLUMN_NAME | COLLATION_NAME |

+--------------+------------+-------------+-----------------+

| test     | cs     | id     | NULL      |

| test     | cs     | name    | utf8_unicode_ci |

+--------------+------------+-------------+-----------------+

2 rows in set (0.00 sec)

可以发现列字符集没有改变，并且只有新的列才会默认继承表的字符集（utf8.utf8_general_ci）。

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