mysql 不允许我更改排序规则类型

Question

我正在尝试将我的 table 归类类型从 unicode 转换为通用，但 mysql 不允许这样做。没有返回任何错误，但是当我查看 table 时，我可以看到没有进行任何更改。

mysql> show variables like '%coll%';
+----------------------+-----------------+
| Variable_name        | Value           |
+----------------------+-----------------+
| collation_connection | utf8_general_ci |
| collation_database   | utf8_unicode_ci |
| collation_server     | utf8_unicode_ci |
+----------------------+-----------------+
3 rows in set (0.00 sec)

mysql> show create table abc;
+----------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table    | Create Table                                                                                                                                                                                                      |
+----------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| abc_test | CREATE TABLE `abc` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `somecolumn` bigint(20) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci ROW_FORMAT=DYNAMIC |
+----------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.01 sec)

mysql> alter table abc convert to charset utf8 collate utf8_general_ci;
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> show create table abc;
+----------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table    | Create Table                                                                                                                                                                                                      |
+----------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| abc_test | CREATE TABLE `abc` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `somecolumn` bigint(20) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci ROW_FORMAT=DYNAMIC |
+----------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

Answer 1

像这样使用改变ALTER TABLE table_name COLLATE='utf8_general_ci';

您的 table 已经有 UTF8 charset。所以，在我看来你不需要再次设置它。我可以看到您正在尝试使用 alter 查询再次将其转换为 charset utf8。

Answer 2

我尝试使用 mysql 5.7.18，一切看起来都很好。那么您使用的是哪个版本？

我设置了与你相同的排序规则变量，并创建了 table 并通过从上面复制的语句更改了排序规则。最后我得到了：

mysql> show create table abc;
+-------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                                                                                                       |
+-------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| abc   | CREATE TABLE `abc` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `somecolumn` bigint(20) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8 ROW_FORMAT=DYNAMIC |
+-------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.01 sec)

mysql> select version();
+--------------+
| version()    |
+--------------+
| 5.7.18-debug |
+--------------+

"SHOW CREATE TABLE" 不打印归类信息，因为 utf8_general_ci 是 utf8 的默认归类。

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