Query For Getting the First Entered Field For Every User - mysql

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

Answer 2

can not test it and it's performance at the moment but I thing u can start from the following query:
SELECT
u.id,
SUBSTRING_INDEX( GROUP_CONCAT(CAST(d.weight AS CHAR) ORDER BY d.date ASC ), ',', 1 ) as starting_weight,
SUBSTRING_INDEX( GROUP_CONCAT(CAST(d.weight AS CHAR) ORDER BY d.date DESC), ',', 1 ) as ending_weight
FROM users as u
LEFT JOIN daily_measurements as d ON (u.id = d.user_id)
edit please treat this as a suggestion for your Query...
with such amount of users "JOIN" could be hundreds times faster then two SELECT sub-queries

Answer 3

SELECT A.user_id,
B.weight InitialWeight,
B.`date` InitialDate,
C.weight LatestWeight,
C.`date` LatestDate
FROM
(
SELECT user_id,MIN(id) idmin,MAX(id) idmax
FROM daily_measurements GROUP BY user_id
) A
INNER JOIN daily_measurements B ON (A.user_id=B.user_id AND A.idmin = B.id)
INNER JOIN daily_measurements C ON (A.user_id=C.user_id AND A.idmax = C.id);
Please make sure you have an index like this
ALTER TABLE daily_measurements ADD UNIQUE INDEX userid_id_ndx (user_id,id);

Answer 4

Try this:
select tb.* from daily_measurements tb
join (
select user_id, MIN(date) firstDate, MAX(date) lastDate
from daily_measurements
group by user_id
) temp
on tb.user_id = temp.user_id
and (tb.date = temp.firstDate or tb.date = temp.lastDate)
The subquery will identify first date and last date rows for each user_id, and main query will fetch the rows again to get all the data.