如果的情况之间存在语句时条件SQL

Question

在我的存储过程的中间，我有下面的代码片断：

case 
    when l.codeleasestatuscode = '5' and priorleaseid is null 
    and l.leaid in(select col1 from Waitlisthousehold) 
then '2' 
else l.codeleasestatuscode 
end 

然而，最后的条件，其中i具有从表Waitlisthousehold选择，有一个问题。并非所有数据库都有该表。所以我希望在表格存在时包含最后一个条件。但当我尝试这样做时，我收到错误：

case 
when l.codeleasestatuscode = '5' and priorleaseid is null 
IF EXISTS(select * from information_schema.tables where table_name='WaitlistHousehold') 
    begin 
    and l.leaid in(select col1 from Waitlisthousehold) 
    end 
then '2' 
else l.codeleasestatuscode 
end 

那么，我该如何正确地做到这一点？

这个片段是内从语句（FROM表1上a.id = b.id和情况下，当一个连接表2 b ..）

Answer 1

你不能使得那样的SELECT语句中添加。你可以这样做：

IF EXISTS(select * from information_schema.tables where table_name='WaitlistHousehold') 
    BEGIN 
    SELECT whatever, 
    case 
    when l.codeleasestatuscode = '5' and priorleaseid is null 
    and l.leaid in(select col1 from Waitlisthousehold) 
    then '2' 
    else l.codeleasestatuscode 
    end AS whatever1 
    FROM wherever 
    END 
ELSE 
    BEGIN 
    SELECT whatever, 
    case 
    when l.codeleasestatuscode = '5' and priorleaseid is null 
    then '2' 
    else l.codeleasestatuscode 
    end AS whatever1 
    FROM wherever 
    END 

Answer 2

你可以有另一种情况，当你第一个内部或检查表中存在不

CASE 
WHEN l.codeleasestatuscode = '5' and priorleaseid is null 
    CASE WHEN EXISTS(SELECT * FROM information_schema.tables WHERE table_name='WaitlistHousehold') 
     THEN 
      CASE WHEN l.leaid in(select col1 from Waitlisthousehold) THEN '2' 
      ELSE l.codeleasestatuscode END 
     ELSE '2' END   
    THEN '2'END 
ELSE l.codeleasestatuscode 
END