Top 1 with a left join

Use OUTER APPLY instead of LEFT JOIN:

SELECT u.id, mbg.marker_value FROM dps_user uOUTER APPLY     (SELECT TOP 1 m.marker_value, um.profile_id     FROM dps_usr_markers um (NOLOCK)         INNER JOIN dps_markers m (NOLOCK)              ON m.marker_id= um.marker_id AND                 m.marker_key = 'moneyBackGuaranteeLength'     WHERE um.profile_id=u.id      ORDER BY m.creation_date    ) AS MBGWHERE u.id = 'u162231993';

Unlike JOIN, APPLY allows you to reference the u.id inside the inner query.

The key to debugging situations like these is to run the subquery/inline view on its' own to see what the output is:

  SELECT TOP 1          dm.marker_value,          dum.profile_id    FROM DPS_USR_MARKERS dum (NOLOCK)    JOIN DPS_MARKERS dm (NOLOCK) ON dm.marker_id= dum.marker_id                                 AND dm.marker_key = 'moneyBackGuaranteeLength'ORDER BY dm.creation_date

Running that, you would see that the profile_id value didn't match the u.id value of u162231993, which would explain why any mbg references would return null (thanks to the left join; you wouldn't get anything if it were an inner join).

You've coded yourself into a corner using TOP, because now you have to tweak the query if you want to run it for other users. A better approach would be:

   SELECT u.id,           x.marker_value      FROM DPS_USER uLEFT JOIN (SELECT dum.profile_id,                  dm.marker_value,                  dm.creation_date             FROM DPS_USR_MARKERS dum (NOLOCK)             JOIN DPS_MARKERS dm (NOLOCK) ON dm.marker_id= dum.marker_id                                          AND dm.marker_key = 'moneyBackGuaranteeLength'           ) x ON x.profile_id = u.id     JOIN (SELECT dum.profile_id,                  MAX(dm.creation_date) 'max_create_date'             FROM DPS_USR_MARKERS dum (NOLOCK)             JOIN DPS_MARKERS dm (NOLOCK) ON dm.marker_id= dum.marker_id                                          AND dm.marker_key = 'moneyBackGuaranteeLength'         GROUP BY dum.profile_id) y ON y.profile_id = x.profile_id                                   AND y.max_create_date = x.creation_date    WHERE u.id = 'u162231993'

With that, you can change the id value in the where clause to check records for any user in the system.

Because the TOP 1 from the ordered sub-query does not have profile_id = 'u162231993'Remove where u.id = 'u162231993' and see results then.

Run the sub-query separately to understand what's going on.