Question

我希望在单个条件为真时显示多个语句，例如SQL中的语句。

例如：

case when (condition is true) then 
print "A" 
print "B"
.
.
.
.
print "Z"
when (condition2 is true) then 
print "Z" 
print "Y"
.
.
.
.
print "A

end

有人能为我提供确切的语法吗？提前谢谢。

Answer 1

如果您的情况很复杂，可以将其移至子查询。这样你就不必为每一列重复它了：

select  case when Condition = 1 then 'A' else 'B' end
,       case when Condition = 1 then 'C' else 'D' end
,       case when Condition = 1 then 'E' else 'F' end
,       ...
from    (
        select  *
        ,       case
                when ... complex condition ... then 1 
                else 0 
                end as Condition
        from    YourTable
        ) as SubQueryAlias

另一种选择是与CTE的联合（在所有数据库中都不可用。）这允许您在没有case的情况下为两者写入表达式，并且由于CTE，条件不会重复。

;       with CteAlias as
        (
        select  *
        ,       case
                when ... complex condition ... then 1 
                else 0 
                end as Condition
        from    YourTable
        )
select  'A', 'C', 'E'
from    CteAlias
where   Condition = 1
union all
select  'B', 'D', 'F'
from    CteAlias
where   Condition = 0

当一个条件为真时，我可以执行多个表达式，例如SQL中的语句吗？

1 个答案: