Question

We are developing something like a social networking website. I’ve got task to do
‘follow me’ functionality. In our website objects are users, teams, companies, channels and groups (please don’t ask why there are groups and teams – it is complicated for me too, but teams are releated to user’s talent)

Users, teams, channels, companies and groups have all their own tables.

I have a query which gets me all the follower’s leaders like this

select
  --fo.leader_id,
  --fo.leader_type,
  us.name as user_name,
  co.name as company_name,
  ch.title as channel_name,
  gr.name as group_name,
  tt.name as team_name
from
  follow_up fo
left join users us
  on (fo.leader_id = us.id and fo.leader_type = 'user')
left join companies co
  on (fo.leader_id = co.user_id and fo.leader_type = 'company')
left join channels ch
  on (fo.leader_id = ch.id and fo.leader_type = 'channel')
left join groups gr
  on (fo.leader_id = gr.id and fo.leader_type = 'group')
left join talent_teams tt
  on (fo.leader_id = tt.id and fo.leader_type = 'team')
where
  follower_id = 83

I need to get all fields like:

• user_name,
• company_name,
• channel_name,
• group_name,
• team_name

as one field in SELECT’s product.
I have tried to alias them all the same ‘name’ but Oracle numbered it.
Please help 🙂

Answer 1

Column names in a query result set must be unique. Perhaps you want one row for each user, company, channel, group and team for the given follower? In which case I’d use a query like this:

select fo.leader_type, us.name
from follow_up fo
join users us
  on (fo.leader_id = us.id and fo.leader_type = 'user')
where follower_id = 83
UNION ALL
select fo.leader_type, co.name
from follow_up fo
join companies co
  on (fo.leader_id = co.user_id and fo.leader_type = 'company')
where follower_id = 83
UNION ALL
select fo.leader_type, ch.title as name
from follow_up fo
join channels ch
  on (fo.leader_id = ch.id and fo.leader_type = 'channel')
where follower_id = 83
UNION ALL
select fo.leader_type, gr.name
from follow_up fo
join groups gr
  on (fo.leader_id = gr.id and fo.leader_type = 'group')
where follower_id = 83
UNION ALL
select fo.leader_type, tt.name
from follow_up fo
join talent_teams tt
  on (fo.leader_id = tt.id and fo.leader_type = 'team')
where follower_id = 83