Question

我有一个场景，如果传递给查询的参数是99999，我需要在where子句中使用多个值，否则我只使用param本身。我使用“IN”作为where子句的一部分，但我得到以下错误“关键字'CASE'附近的语法不正确”。任何一个提供替代不正确的查询，将获得我需要的结果？

DECLARE @IPD_NEWS_TYPE_PARAM decimal (18,0)
 SET @IPD_NEWS_TYPE_PARAM = 99999

SELECT 
    n.id,
    n.headline,
    n.news_type_id
FROM news n
WHERE n.news_type_id IN
CASE WHEN @IPD_NEWS_TYPE_PARAM = 99999 THEN (1,2,3,4,5)
ELSE
(@IPD_NEWS_TYPE_PARAM)
END

Answer 1

也许你想要：

DECLARE @IPD_NEWS_TYPE_PARAM decimal (18,0)
 SET @IPD_NEWS_TYPE_PARAM = 99999

SELECT 
    n.id,
    n.headline,
    n.news_type_id
FROM news n
WHERE (n.news_type_id IN ('1','2','3','4','5') AND @IPD_NEWS_TYPE_PARAM = 99999) 
   OR (n.news_type_id = @IPD_NEWS_TYPE_PARAM AND @IPD_NEWS_TYPE_PARAM <> 99999)

Answer 2

使用IF语句：

DECLARE @IPD_NEWS_TYPE_PARAM decimal (18,0)
 SET @IPD_NEWS_TYPE_PARAM = 99999

IF (@IPD_NEWS_TYPE_PARAM = 99999) 
    SELECT 
        n.id,
        n.headline,
        n.news_type_id
    FROM news n
    WHERE n.news_type_id IN (1,2,3,4,5)
ELSE
    SELECT 
        n.id,
        n.headline,
        n.news_type_id
    FROM news n
    WHERE n.news_type_id = @IPD_NEWS_TYPE_PARAM

Answer 3

您可以使用CASE表达式返回要随后测试的值，例如：

SELECT 
    n.id,
    n.headline,
    n.news_type_id
FROM news n
WHERE CASE
  WHEN @IPD_NEWS_TYPE_PARAM = 99999 THEN
    CASE WHEN n.news_type_id IN (1,2,3,4,5) THEN 1 ELSE 0 END
  WHEN @IPD_NEWS_TYPE_PARAM = n.news_type_id THEN 1
  ELSE 0
  END = 1

带有“where in”子句的case语句

3 个答案: