count number of rows associated with their id in another table - php

Question

Hi We have 3 Table of a music which is something like this in MySql :
1st Table :
the first table is for playlist table where music playlist is exist.
playlistId playlistTitle categoryId
1 hello 0
2 wow 0
3 wi-fi 0
4 awesome 0
5 sixer 1
6 four 1
7 boundary 2
2nd Table :
2nd table is for songRelation table where every playlist is associated with thier song
playlistId songId
1 4
1 3
1 43
1 57
1 98
2 56
2 67
2 90
2 78
3 98
3 78
3 89
43 90
3rd Table : the 3rd table is for song table where song detail exist
songId songTitle
4 hello
3 real hero
43 singalone
57 awesom
98 really
78 sakaka
98 shikwa
89 moha
90 hello2
67 Sneh
actually i am fetching the result something like this:
playlistId songId categoryId songTitle
1 4 0 hello
1 3 0 real hero
2 56 0 singalone
2 67 0 Sneh
3 78 0 sakaka
3 98 0 Shikwa
where the every playlistId will be with their first 2songIdand with theircategoryIdand also withsongTitle`.
but i want to count the total song with every playlistId
after getting the total song result i want will be something like this :
playlistId songId categoryId songTitle totalSong
1 4 0 hello 5
1 3 0 real hero 5
2 56 0 singalone 4
2 67 0 Sneh 4
3 78 0 sakaka 3
3 98 0 Shikwa 3
here is the jsfiddle Demo where query is without totalSong http://sqlfiddle.com/#!9/7eda7/5
What subquery will be added to get the above desired result.

Answer 1

To get exactly the result you asked, use this:
select p.playlistId,
s.songId,
p.categoryId,
s.songTitle,
(select count(*) from songRelation where playlistId = p.playlistId) totalSong
from playlist p
inner join songRelation r on p.playlistId = r.playlistId
inner join song s on r.songId = s.songId
Using a group by on the main query would merge the detailed song data, forcing you to run two queries: one for details (first 4 fields) and a second query, to recover the totals (last column). Using this solution, you get all detailed data and totals, the sub-query will recover the count of songs for each playlist, the way you asked.
UPDATE:
This way, suggested by rlanvin, should make the query faster, because instead on computing the subquery for each row, it gets computed only once, and then is joined to the main query. The result is the same:
select p.playlistId,
s.songId,
p.categoryId,
s.songTitle,
r1.totalSong
from playlist p
inner join songRelation r on p.playlistId = r.playlistId
inner join song s on r.songId = s.songId
inner join (SELECT playlistid, COUNT(songId) as totalSong from songRelation group by playlistid) r1 on p.playlistId = r1.playlistId

Answer 2

I have added this query to ur SQLFIDDLE.
SELECT p.playlistId, s.songId, p.categoryId, s.songTitle,
(select count(sr1.songId) from songRelation sr1
where sr1.playlistid=p.playlistid
group by sr1.playlistId) as total,
#r := IF (#pid = p.playlistId,
IF (#pid := p.playlistId, #r+1, #r+1),
IF (#pid := p.playlistId, 1, 1)) AS rn
FROM playlist AS p
CROSS JOIN (SELECT #r:=0, #pid:=0) AS vars
INNER JOIN songRelation AS sr ON p.playlistId = sr.playlistId
INNER JOIN song AS s ON sr.songid = s.songid
ORDER BY p.playlistId, s.songId ) AS t
WHERE t.rn <= 2
It is giving the required output. Check the Demo Here

Answer 3

Using Group Functions you can do this:
SELECT `playlistid`, COUNT(`songid`)
FROM `playlist`
GROUP BY `playlistid`