Question

我有一个where子句，我需要在其中添加case语句，并且必须在then和else内给出条件语句。

我的状况看起来像这样

WHERE 
    CASE
        WHEN 
        Substring(datename(dw,getdate()),1,3) = 'mon' 
        THEN convert(varchar,dt_start,103) = convert(varchar,dateadd(day,-3,getdate()),103) 
        AND  convert(varchar,dt_start,103) <= convert(varchar,dateadd(day,-2,getdate()),103)
        ELSE convert(varchar,dt_start,103) = convert(varchar,dateadd(day,-1,getdate()),103)
    END

但是此查询显示=内then处的语法错误。相同的逻辑在PostgreSQL中有效，但是当我在SQL Server中尝试时，它在=处出现语法错误。我如何解决这个问题。请帮忙
这是相应的PGSQL查询。

WHERE 
    CASE
        WHEN to_char(now(), 'dy'::text) = 'mon'::text THEN to_char(dt_start, 'yyyymmdd'::text) = to_char(now() - '3 days'::interval, 'yyyymmdd'::text) AND to_char(dt_start, 'yyyymmdd'::text) <= to_char(now() - '2 days'::interval, 'yyyymmdd'::text)
        ELSE to_char(dt_start, 'yyyymmdd'::text) = to_char(now() - '1 day'::interval, 'yyyymmdd'::text)
    END

Answer 1

尝试

WHERE 
convert(varchar,dt_start,103)=
CASE
    WHEN 
    Substring(datename(dw,getdate()),1,3) = 'mon' 
    THEN convert(varchar,dt_start,103) = 
    convert(varchar,dateadd(day,-3,getdate()),103) 
    ELSE convert(varchar,dt_start,103) = 
    convert(varchar,dateadd(day,-1,getdate()),103)
END  

AND

convert(varchar,dt_start,103)<=
CASE
 WHEN 
 Substring(datename(dw,getdate()),1,3) = 'mon' 
  then convert(varchar,dateadd(day,-2,getdate()),103)
  else
  --put a condition that does not filter any data (maybe)
  convert(varchar,getdate(),103)
  end

Answer 2

请尝试：您必须根据自己的要求制定两个单独的条件，并记住其中一项，您只能以CASE的身份开始WHERE a = CASE，而不能以WHERE CASE ...THEN a = b+c ...身份开始或在这种情况下，我建议您使用动态查询，在这种情况下，根据不同条件操作查询非常容易

WHERE convert(varchar,dt_start,103) =
    CASE WHEN Substring(datename(dw,getdate()),1,3) = 'mon' THEN 
        convert(varchar,dateadd(day,-3,getdate()),103) 
    ELSE 
        convert(varchar,dateadd(day,-1,getdate()),103) 
    END

    AND convert(varchar,dt_start,103) <= 
    CASE WHEN Substring(datename(dw,getdate()),1,3) = 'mon' THEN
        convert(varchar,dateadd(day,-2,getdate()),103)
    ELSE 
        convert(varchar,dt_start,103)
    END

在where条件中添加case语句，然后在then子句中提供条件语句

2 个答案: