mysql - MySQL 默认使用什么排序规则进行 ORDER BY？

Question

这些查询都给出了我期望的结果:

SELECT sex
FROM ponies
ORDER BY sex COLLATE latin1_swedish_ci ASC

SELECT sex
FROM ponies
ORDER BY CONVERT(sex USING utf8) COLLATE utf8_general_ci ASC

| f |
| f |
| m |
| m |
+---+

但是这个查询给出了不同的结果:

SELECT sex FROM ponies ORDER BY sex ASC

| m |
| m |
| f |
| f |
+---+

这是配置:

SHOW VARIABLES LIKE 'collation\_%'

| collation_connection | utf8_general_ci   |
| collation_database   | latin1_swedish_ci |
| collation_server     | latin1_swedish_ci |
+----------------------+-------------------+

表格排序规则为 latin1_swedish_ci。

MySQL 服务器是 5.5.16。

Answer 1

表格排序规则

排序规则默认值是逐个表存储的。有一个服务器设置的默认值，但该默认值在创建表时应用于表。

要查找特定表的排序规则，请运行以下查询:

SHOW TABLE STATUS LIKE 'ponies'\G

您应该看到如下输出:

*************************** 1. row ***************************
           Name: ponies
         Engine: MyISAM
        Version: 10
     Row_format: Fixed
           Rows: 8
 Avg_row_length: 20
    Data_length: 160
Max_data_length: 5629499534213119
   Index_length: 1024
      Data_free: 0
 Auto_increment: NULL
    Create_time: 2012-02-27 10:16:25
    Update_time: 2012-02-27 10:17:40
     Check_time: NULL
      Collation: latin1_swedish_ci
       Checksum: NULL
 Create_options: 
        Comment: 
1 row in set (0.00 sec)

您可以在该结果中看到排序规则设置。

列排序规则

您还可以覆盖表中特定列的排序规则设置。像这样的创建表语句将创建一个 latin1_swedish_ci 表，其中包含 utf8_polish_ci 列:

CREATE TABLE ponies (
    sex CHAR(1) COLLATE utf8_polish_ci
) CHARACTER SET latin1 COLLATE latin1_swedish_ci;

查看结果的最佳方式如下:

SHOW FULL COLUMNS FROM ponies;

输出:

+-------+---------+----------------+------+-----+---------+-------+---------------------------------+---------+
| Field | Type    | Collation      | Null | Key | Default | Extra | Privileges                      | Comment |
+-------+---------+----------------+------+-----+---------+-------+---------------------------------+---------+
| sex   | char(1) | utf8_polish_ci | YES  |     | NULL    |       | select,insert,update,references |         |
+-------+---------+----------------+------+-----+---------+-------+---------------------------------+---------+
1 row in set (0.00 sec)