ISNULL，SQL，使用select语句作为第二个参数

Question

我不知道这在 SQL 中是否可行，或者我是否必须编写一个存储过程，但我尝试使用 ISNULL 函数，如下所示，以便当参数 @sku 为 null 时，我使用 select 语句来引入返回表中的所有 sku：

SELECT     GooglePrice.idGooglePrice, GooglePrice.idProduct,  products.sku, products.wholeprice, products.price as CurrentHMMPrice, GooglePrice.bestPrice, GooglePrice.link, GooglePrice.title, GooglePrice.description, GooglePrice.ourPrice as PriceCompHMMPrice, 
                      GooglePrice.searchType, GooglePrice.shippingCost, GooglePrice.cheapestOrder, GooglePrice.timeStamp, 
    'ShippingCostNew' = CASE
        WHEN GooglePrice.shippingCost = -1 THEN 'N/A'
        WHEN GooglePrice.shippingCost = 0 THEN 'Free Shipping'
        WHEN GooglePrice.shippingCost > 0 Then cast(GooglePrice.shippingCost as varchar)
        END
FROM         GooglePrice INNER JOIN
                      products ON GooglePrice.idProduct = products.idProduct
WHERE     (products.supplierCode in (@SupplierCode)) AND ISNULL((products.sku like '%'+@sku+'%'), (products.sku in (select sku from products where products.sku)))

ORDER BY GooglePrice.idGooglePrice

Answer 1

用 OR 会更容易

WHERE
     (products.supplierCode in (@SupplierCode)) 
     AND 
     (products.sku like '%'+@SupplierCode+'%' OR @SupplierCode IS NULL)

这是你的意图，不是吗？

     AND 
     products.sku like ISNULL('%'+@SupplierCode+'%',products.sku)

注意：

• 前导通配符无法优化，也不会使用索引。
• 我假设您在 @SupplierCode 中没有此 products.supplierCode in (@SupplierCode) 的 CSV

Answer 2

不要把它搞得太复杂。

创建您的 WHERE 子句：

WHERE     
   ((products.supplierCode in (@SupplierCode)
       AND 
   (products.sku like '%'+@SupplierCode+'%'))
OR (@suppliercode IS NULL)

您并没有真正解释您的逻辑，所以我猜测，但想法是对 NULL 比较进行单独检查。

Answer 3

SELECT GooglePrice.idGooglePrice, GooglePrice.idProduct,  products.sku, products.wholeprice, products.price as CurrentHMMPrice, GooglePrice.bestPrice, GooglePrice.link, GooglePrice.title, GooglePrice.description, GooglePrice.ourPrice as PriceCompHMMPrice, GooglePrice.searchType, GooglePrice.shippingCost, GooglePrice.cheapestOrder, GooglePrice.timeStamp, 
    'ShippingCostNew' = CASE
        WHEN GooglePrice.shippingCost = -1 THEN 'N/A'
        WHEN GooglePrice.shippingCost = 0 THEN 'Free Shipping'
        WHEN GooglePrice.shippingCost > 0 Then cast(GooglePrice.shippingCost as varchar)
        END
FROM  GooglePrice INNER JOIN
      products ON GooglePrice.idProduct = products.idProduct
WHERE (products.supplierCode in (@SupplierCode)) AND (@SupplierCode is null or products.sku like '%'+@SupplierCode+'%')
ORDER BY GooglePrice.idGooglePrice