Question

I’ve a table called tbl_users

================================================================================
system_name | user_id | username | password | system_id | group_id | user_level
================================================================================
Demo        | 12345   | demo     | demo     | 99999     | 54321    | Admin
================================================================================
Demo        | 78794   | demo2    | demo2    | 99999     |          | Employee
================================================================================

And second table as tbl_groups

=================================
system_id | group_id | group_name
=================================
99999     | 54321    | engine     
=================================

Am using this query :

SELECT username, user_level, system_name, tbl_users.system_id, tbl_users.user_id, tbl_users.group_id, group_name 
FROM tbl_users JOIN tbl_groups 
WHERE tbl_users.group_id = tbl_groups.group_id 
AND system_name = 'demo' 
AND tbl_users.system_id = '99999'

But using the above query am just getting a row of Demo User, I want Demo 2 also but can’t get it done, If am removing tbl_users.group_id = tbl_groups.group_id I get both rows but in group_name it’s printed engine in Demo2 User group_name column which is wrong as he has no group currently, so how can I query that I get all users and names of groups if a user is in or else I want group_name column blank if user is in no group.

Answer 1

You are looking for an OUTER JOIN:

FROM tbl_users 
LEFT OUTER JOIN tbl_groups 
  ON tbl_users.group_id = tbl_groups.group_id
WHERE ...