Question

我希望在变量具有值的条件下执行WHERE子句的一部分。我曾尝试用许多不同的方式写这个，但总是遇到错误，并想知道是否有人可以提供帮助。

下面的代码是我当前的SQL语句，但如果我的@itemId为空，则不会返回任何内容。如果将@itemId作为值，我只想减少结果。

DECLARE @itemId nvarchar(max)
SET @itemId = 'someId'

SELECT
SalesOrdersItems.Id,
CASE
    WHEN SalesOrderItems.ItemType = 'P' THEN Products.ProductId
    WHEN SalesOrderItems.ItemType = 'S' THEN Sundries.SundryId
    WHEN SalesOrderItems.ItemType = 'F' THEN FreightMethods.FreightMethodId
    ELSE SalesOrderItems.FreeTextItem
END AS ItemId
FROM SalesOrderItems
    LEFT OUTER JOIN Products ON SalesOrderItems.Product = Products.Product
    LEFT OUTER JOIN Sundries ON SalesOrderItems.Sundry = Sundries.Sundry
    LEFT OUTER JOIN FreightMethods ON SalesOrderItems.FreightMethod = FreightMethods.FreightMethod
WHERE 
SalesOrdersItems.area LIKE 'SE%'
AND (Products.ProductId = @itemId OR Sundries.SundryId = @itemId OR FreightMethods.FreightMethodId = @itemId OR SalesOrderItems.FreeTextItem = @itemId)

我尝试过像这样编写最后一行（参见下面的代码），但它不起作用。

AND CASE 
        WHEN @itemId = '' THEN 1
        ELSE (Products.ProductId = @itemId OR Sundries.SundryId = @itemId OR FreightMethods.FreightMethodId = @itemId OR SalesOrderItems.FreeTextItem = @itemId)
    END

有没有人有任何想法我错了？

Answer 1

如果我误会请告诉我，我假设如果你有一个空白的@itemID，你想要所有的结果，否则你会限制结果。

WHERE SalesOrdersItems.area LIKE 'SE%' 
AND ((@itemId != '' 
    AND (Products.ProductId = @itemId 
         OR Sundries.SundryId = @itemId 
         OR FreightMethods.FreightMethodId = @itemId 
         OR SalesOrderItems.FreeTextItem = @itemId)) 
    OR @itemId = '')

我相信我的parens是正确的，但他们可能是不平衡的。希望清楚地了解我的意图。

Answer 2

...
WHERE
1 = CASE WHEN ... THEN 1 ELSE 0 END
...

Answer 3

您可以使用NULLIF()

AND CASE 
        WHEN NULLIF(@itemId, '') IS NULL THEN 1
        ELSE (Products.ProductId = @itemId OR Sundries.SundryId = @itemId OR FreightMethods.FreightMethodId = @itemId OR SalesOrderItems.FreeTextItem = @itemId)
    END

Answer 4

根据我的理解，你应该做类似下面的事情。

     (Products.ProductId = @itemId OR ISNULL(@itemId, '') = '') OR 
     (Sundries.SundryId = @itemId OR ISNULL(@itemId, '') = '') OR 
     (FreightMethods.FreightMethodId = @itemId OR ISNULL(@itemId, '') = '') OR 
     (FreightMethods.FreeTextItem = @itemId OR ISNULL(@itemId, '') = '')

希望这会有所帮助!!

SQL：如果var =''不执行任何操作，则向WHERE子句添加条件

4 个答案: