I have a table with uuid and system column. I need a query to return only uuid's having system=1 but not the uuids with system= 1 nad 2

Question

I have a table with uuid and system column. I need a query to return only uuid's having system=1 but not the uuids with system= 1 and 2

Answer 1

SELECT  *
FROM    mytable m
WHERE   system = 1
        AND NOT EXISTS
        (
        SELECT  NULL
        FROM    mytable mi
        WHERE   mi.uuid = m.uuid
                AND mi.system = 2
        )