Question

在我的存储过程中，我有以下代码片段：

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，最后条件，其中我必须从表Waitlisthousehold中选择，有一个问题。并非所有数据库都有该表。所以我希望在表存在时包含最后一个条件。但是当我尝试这样做时，我遇到了错误：

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

那我该怎么做呢？

这个片段位于from语句中（来自table1 a.id = b.id上的连接table2 b以及...时的情况）

Answer 1

你可以在你的一个中有另一个case子句来检查表是否存在

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

Answer 2

你不能在select语句中添加if。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

如果在条件sql的情况下存在语句

2 个答案: