Question

我有一个问题组表，如下所示：

ID, NAME, DESCRIPTION, VERSION_ID

版本表列是：

ID, NUMBER, VERSION_STATE

VERSION_STATE是枚举的，可以是0,1或2.

我需要选择其版本具有v VERSION_STATE 0或1的所有问题组，但如果有问题组且VERSION_STATE = 0我不必返回问题组使用VERSION_STATE = 1。

最简单的方法是：

SELECT distinct QG.id FROM healthsafety.hs_questions_group QG
LEFT OUTER JOIN (SELECT * FROM healthsafety.hs_version) VERSION
ON QG.VERSION_ID = VERSION.ID
WHERE 
VERSION.VERSION_STATE=0
OR VERSION.VERSION_STATE=1

问题是此查询返回所有问题组VERSION_STATE 0或1.如果我删除or子句，并且没有VERSION_STATE = 0的问题组，我需要返回问题VERSION_STATE = 1的小组。

我认为我需要一个if else或case声明，但我被困了。有什么想法吗？

请注意，我必须使用条件来实现此功能，因此我需要使用最简单的解决方案。

Answer 1

SELECT * 
FROM (

SELECT OG.ID,OG.NAME,OG.DESCRIPTION,VERSION.ID,VERSION.NUMBER,VERSION.VERSION_STATE,ROW_NUMBER()OVER(PARTITION BY OG.ID ORDER BY VERSION.VERSION_STATE ASC) as INDICATOR
FROM healthsafety.hs_questions_group QG
LEFT OUTER JOIN 
(SELECT * FROM healthsafety.hs_version) VERSION
ON QG.VERSION_ID = VERSION.ID
WHERE 
VERSION.VERSION_STATE=0
OR VERSION.VERSION_STATE=1
) AS ABC

WHERE (ABC.VERSION_STATE = 0 and ABC.INDICATOR = 1) 
OR (ABC.VERSION_STATE = 1 and ABC.INDICATOR = 1)

Answer 2

使用common table expression和union all，其中第二个查询使用not exists()仅返回version_state=1的行，而version_state=0行不存在。< / p>

;with cte as (
  select qg.id, v.version_state
  from healthsafety.hs_questions_group qg
    inner join healthsafety.hs_version version v
      on qg.version_id = v.id
  where v.version_state in (0,1)
)
select id
from cte
where version_state = 0

union all

select qg.id
from cte
where version_state = 1
  and not exists (
    select 1
    from cte
    where version_state = 0
)

选择拖曳不同条件的值

2 个答案: