MySQL-mysql 条件语句中不能使用当前查询的字段别名来做条件

Question

例如以下sql:

SELECT active_id,user_id,DAYNAME(t) AS t_day FROM active WHERE t_day = 'Sunday' or t_day = 'Saturday'

Answer 1

参考一下Problems with Column Aliases，Can you use an alias in the WHERE clause in mysql?，我写一个通过子查询来实现，测试通过：

 SELECT active_id, t_day FROM (SELECT active_id,user_id,DAYNAME(t) AS t_day FROM active) s WHERE t_day = 'Sunday' OR t_day = 'Saturday';

Answer 2

 select `name` as `sname` from table1 having (`sname`='X信息通');