在sql where子句中执行"if"类​​型语句

Question

我试图在where子句中做一些"if"语句.我意识到sql不支持这个,但我确信必须有一些方法可以使用sql语法.如我在粗体区域所示,我试图找到所有以d开头的项目,如果他们的userfld2也是容器,则将其过滤掉.

有没有一种比我正在做的更合理的方式来做这件事还是我离开了标记？

提前致谢.

Select a.ItemID
   , b.ConversionFactor VCaseAmt
   , sum(c.ConversionFactor + 1) SCaseAmt
   , a.status
   , a.UserFld2
From timItem a
inner join timItemUnitOfMeas b on a.ItemKey = b.ItemKey
   and b.TargetUnitMeasKey = 115
left join timItemUnitOfMeas c on a.ItemKey = c.ItemKey
   and c.TargetUnitMeasKey = 116
left join timItemUnitOfMeas d on a.ItemKey = d.ItemKey
   and d.TargetUnitMeasKey = 126
Where d.TargetUnitMeasKey is null
   and b.ConversionFactor != c.ConversionFactor + 1
   and a.Status = 1
   and **(filter a.itemid not like 'd%' when a.userfld2 = 'Container')**
Group by a.ItemID, b.TargetUnitMeasKey, b.ConversionFactor, C.TargetUnitMeasKey
   , c.ConversionFactor, a.status, a.UserFld2
Order by a.ItemID

Answer 1

用这个：

Select a.ItemID, b.ConversionFactor VCaseAmt, sum(c.ConversionFactor + 1) SCaseAmt, a.status, a.UserFld2

From timItem a inner join
    timItemUnitOfMeas b on a.ItemKey = b.ItemKey and b.TargetUnitMeasKey = 115 left join
    timItemUnitOfMeas c on a.ItemKey = c.ItemKey and c.TargetUnitMeasKey = 116 left join
    timItemUnitOfMeas d on a.ItemKey = d.ItemKey and d.TargetUnitMeasKey = 126

Where d.TargetUnitMeasKey is null and b.ConversionFactor != c.ConversionFactor + 1 and a.Status = 1 and 
not (a.itemid like 'd%' AND a.userfld2 = 'Container') 

Group by a.ItemID, b.TargetUnitMeasKey, b.ConversionFactor, C.TargetUnitMeasKey, c.ConversionFactor, a.status, a.UserFld2

Order by a.ItemID