帶CASE語句的多個條件

Question

我需要查詢一些數據。這裏是我構建的查詢，但這對我來說並不合適。對於這個例子我使用AdventureWorks數據庫。

SELECT * FROM [Purchasing].[Vendor] WHERE PurchasingWebServiceURL LIKE 
case 
// In this case I need all rows to be returned if @url is '' or 'ALL' or NULL 
when (@url IS null OR @url = '' OR @url = 'ALL') then ('''%'' AND PurchasingWebServiceURL IS NULL') 
//I need all records which are blank here including nulls 
     when (@url = 'blank') then (''''' AND PurchasingWebServiceURL IS NULL') 
//n this condition I need all record which are not like a particular value 
     when (@url = 'fail') then ('''%'' AND PurchasingWebServiceURL NOT LIKE ''%treyresearch%''') 
//Else Match the records which are `LIKE` the input value 
     else '%' + @url + '%' 
    end 

這不適合我。如何在同一CASE的THEN中有多個條件條款？我該如何做這項工作？

Answer 1

基於amadan另一種方式：

SELECT * FROM [Purchasing].[Vendor] WHERE 

     ((@url IS null OR @url = '' OR @url = 'ALL') and PurchasingWebServiceURL LIKE '%') 
    or 

     (@url = 'blank' and PurchasingWebServiceURL = '') 
    or 
     (@url = 'fail' and PurchasingWebServiceURL NOT LIKE '%treyresearch%') 
    or((@url not in ('fail','blank','','ALL') and @url is not null and 
      PurchasingWebServiceUrl Like '%'+@ur+'%') 
END 

Answer 2

這不是剪切和粘貼。 CASE表達式必須返回一個值，並返回一個包含SQL的字符串（這在技術上是一個值，但類型錯誤）。這是你想寫什麼，我想：

SELECT * FROM [Purchasing].[Vendor] WHERE 
CASE 
    WHEN @url IS null OR @url = '' OR @url = 'ALL' 
    THEN PurchasingWebServiceURL LIKE '%' 
    WHEN @url = 'blank' 
    THEN PurchasingWebServiceURL = '' 
    WHEN @url = 'fail' 
    THEN PurchasingWebServiceURL NOT LIKE '%treyresearch%' 
    ELSE PurchasingWebServiceURL = '%' + @url + '%' 
END 

我也懷疑，這可能不是在某些方言的工作，但現在不能測試（甲骨文，我看着你），由於不有布爾人。

但是，由於@url不依賴於表值，所以爲什麼不做三個不同的查詢，並根據您的參數選擇要評估哪個？