Question

我有2个数据库表，我想根据公共列之间的匹配更新第一个表。这是我的代码：

update Table1
set comment = 'Valid stuff'
where Name in (
               SELECT T1.name
               FROM Table1 AS T1
               INNER JOIN Table AS T2
                 on T1.name = t2.name
                 and T1.id = T2.id)

如果没有匹配，则应添加其他值，例如“坏东西”。你认为这是我应该做的最好的事情吗？

Answer 1

也许就是这样：

UPDATE T1
SET comment = CASE WHEN ou.name IS NULL THEN 'bad stuff' ELSE 'Valid stuff' END
FROM Table1 T1
OUTER APPLY (SELECT T2.name
             FROM Table T2
             WHERE T1.name = t2.name AND T1.id = T2.id) ou

Answer 2

更好的是：

update t1 set comment = 
  case when exists 
      (Select * from Table 
       Where id = t1.id
          and name = t1.name)
    then 'Valid stuff'
    else 'bad stuff' end
from table1 t1

比较两个SQL Server表中的值，然后根据条件进行更新

2 个答案: