错误缘由:两个表join的时候,不支持两个表的字段的 非相等 操做。sql
解决办法:
一、把不相等条件拿到where语句中segmentfault
select ... from class_order t1 left join class_order_refund t2 on t1.orderdate>t2.orderdate
能够改写成学习
select ... from class_order t1 left join class_order_refund t2 where t1.orderdate>t2.orderdate
二、若是第一中方法不适用,能够在select字段中判断区块链
select ... if(t1.orderdate>t2.orderdate,0,1) as is_refund ... from class_order t1 left join class_order_refund t2 on t1.orderdate>t2.orderdate