mySQL group_concat max dates based on other column - php

Question

I have input table:
+-----+------------+---------------------+---------+-------------+
| id | client_id | subscription_date | program |how_long_subs|
+-----+------------+---------------------+---------+-------------+
| 1 | 1 | 2016-05-20 00:00:00 | W90 | 12 |
| 2 | 4 | 2017-01-01 00:00:00 | W90 | 6 |
| 314 | 7 | 2017-03-21 00:00:00 | AB | 12 |
| 3 | 8 | 2016-12-19 00:00:00 | W90 | 12 |
| 4 | 9 | 2018-06-08 00:00:00 | W90 | 12 |
| 5 | 10 | 2017-06-12 00:00:00 | W90 | 12 |
| 313 | 10 | 2017-01-18 00:00:00 | AB | 12 |
| 377 | 11 | 2018-12-22 00:00:00 | AB | 12 |
| 308 | 11 | 2017-12-22 00:00:00 | AB | 12 |
| 6 | 11 | 2017-12-22 00:00:00 | W90 | 12 |
| 7 | 13 | 2017-01-05 00:00:00 | W90 | 6 |
| 8 | 21 | 2017-03-10 00:00:00 | W90 | 12 |
| 325 | 22 | 2017-03-02 00:00:00 | AB | 1 |
+-----+------------+---------------------+---------+-------------+
id is unique autoincremented column for this table client_id is to connect with clients table. I am looking for a result in form:
+------------+----------+-----------------------------------------+--------+
| client_id | programs | dates |how_long|
+------------+----------+-----------------------------------------+--------+
| 1 | W90 | 2016-05-20 00:00:00 | 12 |
| ... | | | |
| 11 | W90|AB | 2017-12-22 00:00:00|2018-12-22 00:00:00 | 12|12 |
+------------+----------+-----------------------------------------+--------+
so every client_id has 3 columns: programs, dates, how_long
so far I have below for columns programy and na_ile
SELECT
client_id,
GROUP_CONCAT(DISTINCT program SEPARATOR '|') AS programs
FROM subscriptions GROUP BY client_id
but I have no idea how to do this for dates, so everything is in good order.
in example result I chose some client that has multiple rows for different programs, to best illustrate, as you can see dates in result are MAX date for certain program.
To give you better picture what I'm trying to do is process my input table, to be able to calculate remaining subscription for different programs.
Formula is:
if client_id has no records in subscriptions then use date from clients table
and return difference between that date +1 year and today.
if client_id has records in subscriptions then
for every unique program client has in subs table:
get max subscription_date and corresponding how_long_subs for that max date/program. add how_long_subs months to subscription date and return difference from now in days.
My plan is to get result table as described above and use php to process rows to get something like this:
example result for client_id: 11
W90: 2017-12-22 00:00:00 +12 months - now()
AB: 2018-12-22 00:00:00 +12 months - now()
Can you please help me with mySQL query and advice if approach im taking is ok or maybe there is some much easier way of doing it.
Thank you

Answer 1

SELECT A.client_id,
GROUP_CONCAT(DISTINCT A.program SEPARATOR '|') programs,
GROUP_CONCAT(DISTINCT A.subscription_date SEPARATOR '|') dates,
GROUP_CONCAT(A.how_long_subs SEPARATOR '|') how_long
FROM
(SELECT client_id, subscription_date, MAX(program) program, how_long_subs
FROM subscriptions
GROUP BY client_id, subscription_date,how_long_subs) A
GROUP BY A.client_id;
See DEMO on SQL Fiddle.

Answer 2

You could use a subquery for get the max date
SELECT client_id, GROUP_CONCAT( program SEPARATOR '|') programs,
GROUP_CONCAT(max_date SEPARATOR '|') max_date
FROM (
SELECT
client_id,
programs,
max(subscription_date) max_date
FROM subscriptions
GROUP BY client_id, program )