Question

I have a MYSQL Table with the following structure called daily_measurements

+------------+----------+------+-----+---------------------+----------------+
| Field      | Type     | Null | Key | Default             | Extra          |
+------------+----------+------+-----+---------------------+----------------+
| id         | int(11)  | NO   | PRI | NULL                | auto_increment |
| user_id    | int(11)  | NO   |     | 0                   |                |
| date       | datetime | NO   | MUL | 0000-00-00 00:00:00 |                |
| weight     | float    | NO   |     | 0                   |                |
| bicep      | float    | NO   |     | 0                   |                |
| chest      | float    | NO   |     | 0                   |                |
| waist      | float    | NO   |     | 0                   |                |
| neck       | float    | NO   |     | 0                   |                |
| thigh      | float    | NO   |     | 0                   |                |
| hips       | float    | NO   |     | 0                   |                |
| shoulders  | float    | NO   |     | 0                   |                |
| knee       | float    | NO   |     | 0                   |                |
| ankle      | float    | NO   |     | 0                   |                |
| created_on | datetime | NO   |     | 0000-00-00 00:00:00 |                |
+------------+----------+------+-----+---------------------+----------------+

I need to retrieve a list of every user’s weight for there first and last entry.

I’ve tried various combinations of GROUP BY, MIN(date), MAX(date), etc. but I can’t seem to figure out a way to do it efficiently.

The only way I’ve been able to get this to work is to do the following query on the users table, w/ 2 subqueries, but since there are aprox 30,000 users and > 200,000 measurements the query chokes up pretty bad.

SELECT u.id,
(SELECT user_id, weight, date FROM daily_measurements WHERE user_id = u.id ORDER BY date DESC limit 1) as starting_weight,
(SELECT user_id, weight, date FROM daily_measurements WHERE user_id = u.id ORDER BY date ASC limit 1) as ending_weight
FROM users u

Any help would be appreciated.

Answer 1

My solution:

SELECT
  u1.user_id,
  u2.first_entry_weight,
  u1.weight             AS last_entry_weight
FROM daily_measurements u1
  INNER JOIN (SELECT
                u1.user_id,
                u1.weight              AS first_entry_weight,
                u2.fe,
                u2.le
              FROM daily_measurements u1
                INNER JOIN (SELECT
                              daily_measurements.user_id,
                              MIN(date_entry)            fe,
                              MAX(date_entry)            le
                            FROM daily_measurements
                            GROUP BY daily_measurements.user_id) u2
                  ON u1.user_id = u2.user_id
                    AND u1.date_entry = u2.fe) u2
    ON u1.user_id = u2.user_id
      AND u1.date_entry = u2.le