Question

我有一个表，其中主键是两列的组合。我想根据我的主键更新多行

StationId   ServerDate          Status
1           2011-05-05 01:00:00 0
1           2011-05-06 01:00:00 1
2           2011-05-05 01:00:00 2

我的更新查询目前看起来像

Update data set status = 1 where StationId = '1' and  ServerDate = '2011-05-05 01:00:00'
Update data set status = 2 where StationId = '1' and  ServerDate = '2011-05-06 01:00:00'

我正在考虑使用CASE语句，但是当key是两个键的组合时，无法确定如何使用它。这是我使用CASE编写的查询。它改变了我的所有行。如果当前记录不属于记录3之类的任何条件，则其更改为默认值0.我希望该记录保留以前的值。

UPDATE data set status = CASE 
   WHEN StationId = '1' and  ServerDate = '2011-05-05 01:00:00' THEN 1 
   WHEN StationId = '1' and  ServerDate = '2011-05-06 01:00:00' THEN 2 
END

Answer 1

这是我使用CASE编写的查询，但我在查询中遇到错误

删除END关键字后的“CASE”，它应该没问题：

UPDATE data 
   SET status = 
     CASE 
       WHEN stationId = '1' and ServerDate = '2011-05-05 01:00:00' THEN 1 
       WHEN stationId = '1' and ServerDate = '2011-05-06 01:00:00' THEN 2 
       WHEN stationId = '2' and ServerDate = '2011-05-05 01:00:00' THEN 3
     END
WHERE stationId IN ('1', '2')
  AND ServerDate in ('2011-05-05 01:00:00', '2011-05-06 01:00:00')

Answer 2

您的查询应该是:(已编辑）

UPDATE data set status = 
(
   CASE 
       WHEN StationId = '1' AND ServerDate = '2011-05-05 01:00:00' THEN 1 
       WHEN StationId = '2' AND ServerDate = '2011-05-06 01:00:00' THEN 2 
    END 
)
WHERE StationId IN ('1','2')

Answer 3

您只需删除最后一个“CASE”

UPDATE data set status = CASE 
   WHEN StationId = '1' and  ServerDate = '2011-05-05 01:00:00' THEN 1 
   WHEN StationId = '1' and  ServerDate = '2011-05-06 01:00:00' THEN 2 
END

Answer 4

当你处理多行时，你可以使StationId成为更快查询的索引。

mysql>CREATE INDEX index_name ON tableName(StationId);

多个更新查询mysql

4 个答案: