Question

I write this statement which works correctly in all cases except one case

SELECT p.priv_no FROM osqs_privileges p,osqs_users_privileges up 
WHERE up.priv_no = p.priv_no AND up.user_no = 54 AND up."GRANT" = 'Y' 
    UNION 
SELECT p.priv_no FROM 
osqs_privileges p,osqs_groups_privileges gp,osqs_users_groups ug,osqs_users_privileges up 
    WHERE gp.priv_no = p.priv_no AND ug.grp_no = gp.grp_no AND ug.user_no = 54 
AND gp.priv_no NOT IN 
    (SELECT priv_no FROM osqs_users_privileges WHERE user_no = 54 AND "GRANT" = 'N');

in a case that osqs_users_privileges have no rows and this statement (SELECT priv_no FROM osqs_users_privileges WHERE user_no = 54 AND “GRANT” = ‘N’) return 0 rows, all the script return 0 rows even if othe select statements returns data. why?

Answer 1

You need to use an OUTER JOIN:

SELECT p.priv_no FROM osqs_privileges p,osqs_users_privileges up 
WHERE up.priv_no = p.priv_no AND up.user_no = 54 AND up."GRANT" = 'Y' 
    UNION 
SELECT p.priv_no 
FROM osqs_privileges p
LEFT JOIN osqs_groups_privileges gp on osqs_users_groups ug on gp.priv_no = p.priv_no
LEFT JOIN osqs_users_privileges up on ug.grp_no = gp.grp_no
WHERE ug.user_no = 54 
AND gp.priv_no NOT IN 
    (SELECT priv_no FROM osqs_users_privileges WHERE user_no = 54 AND "GRANT" = 'N');