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Alias ​​some column names as one field in select oracle join select query

We are developing something like a social networking site. I have a task to make "follow me". On our website, objects are users, teams, companies, channels, and groups (please don't ask why there are groups and teams - it's also difficult for me, but teams give the talent of the user)

Users, Teams, Channels, Companies, and Groups all have their own tables.

I have a query that gives me all follower 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:

  • Username,
  • company_name,
  • CHANNEL_NAME,
  • group_name,
  • TEAM_NAME

as one field in a SELECT product. I tried alias them anyway "name" but Oracle numbered it. Please, help:)

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3 answers


Column names in the query result set must be unique. Perhaps you need one row for each user, company, channel, group, and team for a given follower? In this case, I would 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
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I'm not sure why you need to get them as one field, because you don't need to split the information on the client side? Either way, one way to do it would be:

user_name || '|' || company_name || '|' || channel_name || '|' || group_name || '|' || team_name all_fields

This will give you a delimited field called all_fields. If you have multiple user_name fields from different tables, you can use the same approach:

   table1.user_name || '|' || table2.user_name ... all_user_names


Then you can split the field on the client side.

Personally, I would just do something like this:

    table1.user_name table1_user_name
  , table2.user_name table2_user_name
    ...

In other words, just use a unique column alias for each username.

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I thought and I came up with this solution:

Is it slower than Jeffrey Kemp's solution?

select
  fo.leader_id,
  fo.leader_type,

  case
    when us.subdomain is not null then us.subdomain
    when us2.subdomain is not null then us2.subdomain
    --when co.name is not null then co.name
    when ch.service_url is not null then ch.service_url
    when gr.id is not null then to_char(gr.id)
    when tt.subdomain is not null then tt.subdomain
    else 'nothing!'
    end
    as leader_url,

  case
    when us.name is not null then us.name
    when co.name is not null then co.name
    when ch.title is not null then ch.title
    when gr.name is not null then gr.name
    when tt.name is not null then tt.name
    else 'nothing!'
    end
    as leader_names,

    case
    when us.img_avatar_path is not null then us.img_avatar_path
    when us2.img_avatar_path is not null then us2.img_avatar_path
    --when us.img_avatar_path is not null and fo.leader_id = co.user_id and fo.leader_type = 'company' then us.img_avatar_path
    when ch.default_img is not null then ch.default_img
    when gr.img_avatar_path is not null then gr.img_avatar_path
    when tt.img_avatar_path is not null then tt.img_avatar_path
    else 'nothing!'
    end
    as img_avatar_path,

    case
    when us.img_avatar_x is not null then us.img_avatar_x
    when us2.img_avatar_x is not null then us2.img_avatar_x
    when  ch.default_img_x is not null then ch.default_img_x
    when gr.img_avatar_x is not null then gr.img_avatar_x
    when tt.img_avatar_x is not null then tt.img_avatar_x
    else 0
    end
    as img_avatar_x,

    case
    when us.img_avatar_y is not null then us.img_avatar_y
    when us2.img_avatar_y is not null then us2.img_avatar_y
    when  ch.default_img_y is not null then ch.default_img_y
    when gr.img_avatar_y is not null then gr.img_avatar_y
    when tt.img_avatar_y is not null then tt.img_avatar_y
    else 0
    end
    as img_avatar_y

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 users us2
    on (co.user_id = us2.id)
  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 = :follower_id
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