Question

Consider the following MySQL tables:

APPLICATIONS (contains all applications by all users)

unique_id |  user_id  |  date_of_application  |  date_ended  | score  |  status
--------------------------------------------------------------------------------
1            user_a          2010-09-09          2010-12-24     1.2      Ended
2            user_a          2011-03-03          2011-06-06     1.3      Ended
3            user_a          2011-08-08          2011-10-10     1.0      Ended

4            user_b          2010-09-09          2010-12-24     2.2      Ended
5            user_b          2011-03-03          2011-06-06     1.5      Ended

6            user_a          2012-01-01                                  Active
7            user_b          2012-01-02                                  Active
8            user_c          2012-01-03                                  Active
9            user_d          2012-01-04                                  Active

Desired result:

user_id  |  date_of_application  |  score  |  status
------------------------------------------------------
user_a          2011-01-01           1.0      Active
user_b          2011-01-02           1.5      Active

user_c          2011-01-03           10       Active
user_d          2011-01-04           10       Active

To explain; I want to select/display ALL records that has status = ‘Active’. In addition, those users who are NOT first-time applicants (user_a and user_b) will have their score set to the previous, latest one (see the bolded parts in applications table) with ‘Ended’ status. On the other hand, first-time users (user_c and user_d) will have their score set to 10.

Notes/to reiterate:

• Assume that score for ‘Ended’ applications/records will always be positive and not null
• user_c and user_d are first time applicants
• the applications table will have multiple records of the same users over time, BUT users can only have ONE ‘Active’ application/record at a time

I have the following to start with; this(or a query similar to this) gave me either NULL or 0 values for the score column

SELECT userid_, date_of_application, status,
score = 
(
     SELECT score 
     FROM applications
     WHERE status = 'Ended' AND 
           date_of_application = (SELECT MAX(date_of_application)
                                  FROM applications
                                  WHERE status='Ended')
)

FROM applications

WHERE 
status = 'Active'

ORDER BY 
score ASC,
date_of_application ASC           

What am I missing here?
TIA.

Answer 1

Considering you want the score to be on the basis of latest.
Try this –

SELECT apps.user_id, apps.date_of_application, apps.status,
       IFNULL(
              (SELECT app.score 
              FROM applications app
              WHERE  app.user_id = apps.user_id
              AND app.status = 'Ended' 
              ORDER BY app.date_ended DESC
              LIMIT 1), 10) AS score
FROM applications apps
WHERE  apps.status = 'Active'
ORDER BY apps.score ASC,
         apps.date_of_application ASC