我想在 SQL 中的 case..when 语句中单个条件为真时显示多个语句。
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
谁能给我提供它的确切语法吗?提前致谢。
如果您的条件很复杂,您可以将其移至子查询。这样您就不必为每一列重复它:
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(并非在所有数据库中都可用。)这允许您编写不带 的表达式case
,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