解决Every derived table must have its own aliasSQL报错

1248 - Every derived table must have its own alias（每个派生表都必须有自己的别名）

报错sql:

SELECT count(*) FROM ( SELECT t.id id, t1.id t1_id, t2.id t2_id FROM t_school t LEFT JOIN t_teacher t1 ON t.teacherid = t1.id LEFT JOIN t_user t2 ON t.userid = t2.id WHERE 1 = 1 ) 

执行这条语句就会报错：Every derived table must have its own alias。

简单的SQL构成是：select 字段名 from 表名，上面子查询里面查出来的是数据，没有被当成一个表，使用我们只需要在SQL后面加上AS 表名 给他一个表的名字即可

修改过后的SQL：

SELECT count(*) FROM ( SELECT t.id id, t1.id t1_id, t2.id t2_id FROM t_school t LEFT JOIN t_teacher t1 ON t.teacherid = t1.id LEFT JOIN t_user t2 ON t.userid = t2.id WHERE 1 = 1 ) AS a

加上表名之后即可解决报错了。