mysql出现 You can't specify target table 'xx' for update in FROM clause 0.000 sec

在执行如下更新语句的时候，提示如下问题： You can't specify target table 'outorder' for update in FROM clause 0.000 sec， 大体翻译出来的意思是： 不能先select出同一表中的某些值，再update这个表(在同一语句中)
update outorder set SchoolId = 5,canteenid = 4 where BillId in ( select BillId from outorder where CanteenId = 6 );
解决方案：将查询出来的数据集放在一个表中，类似如下语句
SELECT a.BillId FROM (select BillId from outorder where CanteenId = 6) a
最终的语句调整为如下格式
update outorder set SchoolId = 5,canteenid = 4 where BillId in ( SELECT a.BillId FROM (select BillId from outorder where CanteenId = 6) a );