如果字段不相等，则从另一个表更新mysql

Question

这个查询有什么问题？

update TA,TB
set TA.change = 1,TA.value = TB.value
where
TA.name  = TB.name and TA.value <> TB.value

我想在结核病价值变化时从TB更新TA

Answer 1

您的查询没问题。我会用明确的join编写它：

update TA join
       TB
       on TA.name  = TB.name
     set TA.change = 1,
         TA.value = TB.value
where TA.value <> TB.value;

您可能需要考虑NULL个值：

update TA join
       TB
       on TA.name  = TB.name
     set TA.change = 1,
         TA.value = TB.value
where not (TA.value <=> TB.value);