Select values where tow different conditions - sql

Question

I have a Questions group table like follows:
ID, NAME, DESCRIPTION, VERSION_ID
Versions table columns are:
ID, NUMBER, VERSION_STATE
VERSION_STATE is an enumerated that can be 0, 1 or 2.
I need to select all questions group that its version has thevVERSION_STATE 0 or 1, but if there is a questions group with a VERSION_STATE = 0 I don't have to return the questions group with the VERSION_STATE = 1.
The simplest approach is:
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
The problem is that this query returns all questions group with the VERSION_STATE 0 or 1. If I remove the or clause, and there are not questions groups with VERSION_STATE = 0, I need to return the questions groups with VERSION_STATE = 1.
I think that I need an if else or case statement but I am stucked. Any Idea?
Note that I have to implement this using criteria, so I need to use the simplest solution.

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

Using a common table expression and a union all where the second query uses not exists() to only return rows where version_state=1 when rows with version_state=0 do not exist.
;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
)