Question

I have this MySQL query

SELECT perms.permission_id, perms.long_title, perms.category, gperms.value FROM
acl_permissions AS perms JOIN acl_group_permissions AS gperms ON
(perms.permission_id = gperms.permission_id AND gperms.group_id = 1) WHERE
perms.type IN ('adm', 'cs') AND perms.simple_title NOT IN ('adm_', 'cs_')
ORDER BY perms.long_title

Basically the bit causing problems is in the ON. I want the query to return all rows from perms based on the where criteria regardless of whether there is a row matching gperms.group_id = 1.

gperms.value would ideally just be an empty string if there was no row matching gperms.group_id = 1.

Answer 1

You want to LEFT OUTER JOIN (or LEFT JOIN for short) gperms instead of just a straight join

SELECT perms.permission_id, perms.long_title, perms.category, gperms.value 
FROM acl_permissions AS perms 
LEFT JOIN acl_group_permissions AS gperms 
    ON (perms.permission_id = gperms.permission_id AND gperms.group_id = 1) 
WHERE perms.type IN ('adm', 'cs') 
    AND perms.simple_title NOT IN ('adm_', 'cs_')
ORDER BY perms.long_title

which will return NULL for gperms.value for any row that doesn’t join the gperms on the given condition.

If you want an empty string instead of the NULL you can use IFNULL():

SELECT perms.permission_id, perms.long_title, perms.category, IFNULL(gperms.value,'')