MySql 1248 - Every derived table must have its own alias

执行一个sql语句，报错：1248 - Every derived table must have its own alias

提示说每一个衍生出来的表，必须要有自己的别名

执行子查询的时候，外层查询会将内层的查询当做一张表来处理，所以我们需要给内层的查询加上别名

错误的：

select count(*)

from(

    select

    FROM_UNIXTIME(`user_task`.`CREATE_TIMESTAMP`, "%Y-%m-%d")

    FROM

    r_user_task `user_task`

    LEFT JOIN

    e_task `task` ON `user_task`.`TASK_ID` = `task`.`ID`

    where `user_task`.`COMPLETE_STATUS` = "" and `user_task`.`user_id` =

    group by FROM_UNIXTIME(`user_task`.`CREATE_TIMESTAMP`, "%Y-%m-%d")

)

正确的sql，应该加上别名，如下：

select count(*)

from(

    select

    FROM_UNIXTIME(`user_task`.`CREATE_TIMESTAMP`, "%Y-%m-%d")

    FROM

    r_user_task `user_task`

    LEFT JOIN

    e_task `task` ON `user_task`.`TASK_ID` = `task`.`ID`

    where `user_task`.`COMPLETE_STATUS` = "" and `user_task`.`user_id` =

    group by FROM_UNIXTIME(`user_task`.`CREATE_TIMESTAMP`, "%Y-%m-%d")

) as t

参考：

https://blog.csdn.net/cao478208248/article/details/28122113

巴特西

MySql 1248 - Every derived table must have its own alias

执行子查询的时候，外层查询会将内层的查询当做一张表来处理，所以我们需要给内层的查询加上别名

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