SQLite select if results in other table are more than n
I have the following tables in my database:
sessions mea开发者_JAVA百科surements
-------- ------------
id id
etc. session_id
etc.
I want to do something like
SELECT * FROM sessions IF
(measurements HAS MORE THAN 0 RESULTS WHERE session_id=X)
Is this sort of query possible in sqlite?
Best regards
Am not sure if SQLite supports EXISTS, so I've provided two alternatives:
SELECT *
FROM sessions S
WHERE EXISTS (SELECT 1 FROM measurements WHERE session_is = S.id)
OR
SELECT *
FROM sessions S
WHERE (SELECT COUNT(*) FROM measurements WHERE session_is = S.id) > 0
This will do it:
select * from sessions where (select count(*) from measurements where session_id=X)>0
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