SQL query from two tables ordering results by both tables columns - php

Question

I have two tables for registering out-going phone calls.
First table is people. The scheme is:
-----------------------------------
id | fname | lname | phone_number |
-----------------------------------
1 | John | Black | 132333312 |
2 | Marry | White | 172777441 |
-----------------------------------
Second tables called calls. The scheme is:
----------------------------------------------------------------------
id | scr_phone | dst_phone | dst_public_id | date | notes |
----------------------------------------------------------------------
1 | 555 | 132333312 | 1 | 1.12.2013 | chit-chat |
2 | 555 | 172777441 | 2 | 1.12.2013 | serios talk |
3 | 555 | 172777441 | 2 | 2.12.2013 | conversation|
----------------------------------------------------------------------
I'm displaying list of phones for users not in an alphabetical order but by frequency of calls. So whoever calls from local phone 555 sees at the top the people who he/she calls more often. Here is the MySQL query I use for it:
SELECT p.fname, p.lname, c.notes, COUNT(c.dst_public_id) AS amount
FROM people p
JOIN calls c ON c.dst_public_id = p.id
WHERE phones != ''
GROUP BY p.id
ORDER BY amount DESC, p.lname ASC
As a result I get person number 2 at the top of the phones list and person number 1 is on second place (I count how many calls are for each individual public and order it by that amount). Here is the query result:
--------------------------------
fname | lname | notes | amount |
--------------------------------
Marry | White | | 2 |
John | Black | | 1 |
--------------------------------
This is all good. But I want always to display last note made on last conersation with that person. I can probably make a totally separated MySQL query for each person requesting last record of each and getting the data from that, something like:
SELECT notes FROM calls WHERE dst_public_id = 2 ORDER BY date DESC LIMIT 1
... and then add the result of the first query inside my PHP script, but is there any way to do it with one single query?

Answer 1

You can get the last note with the following MySQL trick, using group_concat() and substring_index():
SELECT p.fname, p.lname, c.notes, COUNT(c.dst_public_id) AS amount,
substring_index(group_concat(notes order by id desc separator '^'), '^', 1) as last_notes
FROM people p JOIN
calls c
ON c.dst_public_id = p.id
WHERE phones != ''
GROUP BY p.id
ORDER BY amount DESC, p.lname ASC;
For this to work, you need a separator character that will never appear in the notes. I have chosen '^' for this purpose.

Answer 2

Can you try this? I haven't tested it as I don't have
SQL in front of me but you should get the idea.
SELECT tbl.notes, tbl.amount, p.fname, p.lname
FROM people p
join
(
select t.dst_public_id, c1.notes, t.cnt as amount
from calls c1 join
(
SELECT c2.dst_public_id, count(c2.id) as cnt, max(c2.id) as id
FROM
calls c2
group by c2.dst_public_id
) t on c1.id = t.id
) tbl on p.id = tbl.dst_public_id
WHERE p.phones != ''
GROUP BY p.id
ORDER BY tbl.amount DESC, p.lname ASC