带CASE语句的多个条件

Question

我需要查询一些数据。这里是我构建的查询，但这对我来说并不合适。对于这个例子我使用AdventureWorks数据库。

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 

这不适合我。如何在同一CASE的THEN中有多个条件条款？我该如何做这项工作？

Answer 1

基于amadan另一种方式：

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

这不是剪切和粘贴。 CASE表达式必须返回一个值，并返回一个包含SQL的字符串（这在技术上是一个值，但类型错误）。这是你想写什么，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 

我也怀疑，这可能不是在某些方言的工作，但现在不能测试（甲骨文，我看着你），由于不有布尔人。

但是，由于@url不依赖于表值，所以为什么不做三个不同的查询，并根据您的参数选择要评估哪个？