Question

我有一个包含8个列的表，包括设备ID，设备读取类型和设备读取日期。这三列看起来像这样： Example Table

我想要做的是删除DevReadType = XX的每一行以及具有匹配DevNum的每一行但DevReadDate小于DevReadType =＆＃39; XX＆＃39;的日期。我还没有能够找到这种复杂条件的任何例子。非常感谢帮助!!

Answer 1

delete from device
   where  DevNum = @devicenum
   and    DevReadType = 'XX'
   and    DevReadDate < @date

你可以先运行select againsr设备表来测试你的where子句：

select * 
from device
    where  DevNum = @devicenum
    and    DevReadType = 'XX'
    and    DevReadDate < @date

Answer 2

如果我理解正确，我会提出以下建议：

DELETE  d
FROM device d
JOIN (
    SELECT DevNum, MAX(DevReadDate) maxDevReadDate
    FROM device
    WHERE devReadType = 'xx'
    GROUP BY DevNum
) b
ON d.DevNum = b.DevNum AND (d.DevReadDate < b.maxDevReadDate OR d.devReadType = 'xx')

SQL删除基于多列的行

2 个答案: