SQL request with a joining condition - mysql

Question

SELECT mairie.city, permission.permission
FROM permission , user_mairie, mairie
WHERE user_mairie.iduser = 1
AND user_mairie.idmairie = mairie.idmairie
CASE user_mairie.idrole
WHEN 2 THEN
JOIN user_permission
ON user_permission.idpermission = permission.idpermission
AND user_permission.iduser = user_mairie.iduser
END
ORDER BY mairie.idmairie, permission.idpermission
I'm trying to get the permissions of a specific user if this user has a specific role.
A "mairie" is a "town hall" in french.
A user can have different roles in different "mairie"s.
If the user on user_mairie has idrole = 2, then we have to go to the table "user_permission" to get it's permissions.
If the user on user_mairie has idrole = 1 then he is admin and he has ALL permissions, but the permissions are not written in user_permission (because user_permission is used only for idrole = 2).
What I want is for example :
if the user_mairie.idrole = 1 :
SELECT *
FROM permission
if the user_mairie.idrole = 2
SELECT *
FROM permission, user_permission
WHERE user_mairie.idrole = 2
AND user_mairie.iduser = user_permission.iduser
AND user_permission.idpermission = permission.idpermission
I could do this using my programming language and making 2 requests, but I'd like to know if in pure SQL, this issue is solvable.
Some datas:
Table permission:
idpermission | permission
1 | permission_1
2 | permission_2
3 | permission_3
Table user_mairie :
iduser | idmairie | idrole
1 | 1 | 1
1 | 2 | 2
Table user_permission :
iduser | idpermission | idmairie
1 | 1 | 2
1 | 3 | 2
Table mairie :
idmarie | city
1 | mairie_1
2 | mairie_2
The result I want (for a given iduser = 1) would be :
mairie_1 : permission_1, permission_2, permission_3
mairie_2 : permission_1, permission_3
Thanks for reading me.

Answer 1

SQL DEMO
First you start with all marie and all permissions
SELECT um.idrole, m.city, p.permission
FROM user_mairie um
JOIN mairie m
ON um.idmairie = m.idmairie
CROSS JOIN permission p
WHERE um.iduser = 1
Now you remove the permission you dont have
WHERE um.iduser = 1
AND ( um.idrole = 1 -- have all permission
OR EXISTS (SELECT up.idpermission
FROM user_permission up
WHERE up.iduser = um.iduser
AND up.idpermission = p.idpermission )
)
OUTPUT

Answer 2

I think you really want LEFT JOIN:
SELECT . . .
FROM user_mairie LEFT um
user_permission up
ON um.iduser = up.iduser LEFT JOIN
permission p
ON up.idpermission = p.idpermission OR
um.idrole = 1 ;
You may not want the condition on idrole.
This gets permissions only for id roles "2".
Notes:
List all the columns you want in the SELECT.
Learn to use proper, explicit, standard JOIN syntax. Never use commas in the FROM clause.
Table aliases make the query easier to write and to read.
Use LEFT JOIN so you can keep all the rows, even when there are no permissions.