关于mysql:MySQL-order-by-简单解析

MySQL order by 简略解析

1. 语句

SELECT distinct first_letter
FROM tb_customer
WHERE (deleted = 0) ORDER BY first_letter = '#' asc,first_letter;

2. 集体了解

order by first_letter = ‘#’ 相当于做了一个判断 first_letter == “#” ? 1 : 0;

3. SQL 残缺写法

SELECT distinct first_letter
FROM tb_customer
WHERE (deleted = 0) ORDER BY if(first_letter = '#',1,0) asc,first_letter asc;

4. 后果

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