Question

I have the following tables:

users
+----------+----------+----------+
| id       | name     | dob      |
+----------+----------+----------+

authentications
+----------+----------+----------+ 
| id       | user_id  | provider |
+----------+----------+----------+

A user, has-many authentications. user_id in the authentications table is a foreign key to the users table.

Im trying to comple the following output:

+---------------+---------------+---------------+---------------+ 
|    user.id    |   user.name   |   user.dob    |       C       |
+---------------+---------------+---------------+---------------+

Here, C is, the count of the users authentications where provider is ‘facebook’. If instead of the count, I could get a boolean value, ie true if authentications are present, false if not, that would be even better.

I cant figure how to go about constructing the query. Any pointers would be much appreciated.

Answer 1

1) This will return the actual count of Authorization of type FB for every user :

`

Select Name UserName, ID UserID, COUNT(FBAuth) FBAuthCount
from Users LEFT JOIN
(Select UserID, COUNT(AuthType) FBAuth from Auth 
Where AuthType = 'FB'
Group by USERID) Auths on (Users.ID = Auths.UserId)
Group by ID, Name

`

2) This will return the flag true or false for every user depending on thier authorization type:

`

Select Name UserName, ID UserID, 
CASE WHEN COUNT(FBAuth) > 0 THEN 'TRUE' ELSE 'FALSE' END FBAuthFLAG
from Users LEFT JOIN 
(Select UserID, COUNT(AuthType) FBAuth from Auth 
Where AuthType = 'FB'
Group by USERID) Auths on (Users.ID = Auths.UserId)
Group by ID, Name

`

Using a join on smaller dataset: faster response.
Finally, I believe this is the one:

`

SELECT users.id,
       users.email,
       users.name,
       users.sid,
       users.created_at,
       ( CASE
           WHEN fb_auth > 0
           THEN 'true'
           ELSE 'false'
         END ) AS facebook
FROM   users
       LEFT JOIN (SELECT authentications.user_id,
                         Count(authentications.provider) fb_auth
                  FROM   authentications
                  WHERE  provider = 'facebook'
                  GROUP  BY user_id) auths
              ON ( users.id = auths.user_id )
GROUP  BY users.id,
          users.email,
          users.name,
          users.sid,
          users.created_at

`