sql - where 子句中的条件“和”取决于现有值？

Question

谁能知道我是否可以根据现有值在where子句中使用“条件'和'”？？我有一个这样的查询：

@declare idProduct int = 1,
@declare idProducType int = null

select 
    tbl.idProduct, tbl.idProductType, tbl.ProductName, tbl.ProductPrice 
from MyTable tbl 
where tbl.idProduct = 1 
    <IF idProductType is not null>
        and tbl.idProductType = SOMEVALUE
    <ELSE>
        do nothing
    <ENDIF>

我需要始终从此查询中获取数据，而不是在条件为假时获取空值。我怎么能在 SQL Server 2008 中这样做？？？

Answer 1

我认为这就是你想要的：

select 
tbl.idProduct, tbl.idProductType, tbl.ProductName, tbl.ProductPrice 
from MyTable tbl 
where tbl.idProduct = 1 and (tbl.idProductType = @idProducType or @idProducType is null)

Answer 2

....
where tbl.idProduct = 1 
  and (CASE WHEN idProductType is not null and tbl.idProductType = SOMEVALUE Then <something> END) = <something>
/

Answer 3

这应该适合你：

@declare idProduct int = 1,
@declare idProducType int = null

SELECT
    tbl.idProduct, tbl.idProductType, tbl.ProductName, tbl.ProductPrice 
FROM MyTable tbl 
WHERE tbl.idProduct = 1 
    AND (CASE WHEN idProductType is not null THEN tbl.idProductType = SOMEVALUE
    END)