get consecutive records in mysql

Question

I have table structure as following

ID           user_id         win 
1              1               1 
2              1               1 
3              1               0 
4              1               1 
5              2               1 
6              2               0 
7              2               0 
8              2               1 
9              1               0 
10             1               1 
11             1               1 
12             1               1 
13             1               1
14             3               1 

I wants to get consecutive wins(win=1) for each users in mysql.like for user_id=1, it should return 4(record id 10,11,12,13), for user_id=2(record id=5), it should return 1.

I can do that in php after retriving record for each user but I don't know how I can do it using query to mysql.

Also what would be better in term of performance, using php or mysql. Any help will be appreciated.Thanks!!!

Answer 1

Inner query counts each streak. Outer query gets the max per user. Query is untested (but based on one that works)

set @user_id = null;
set @streak = 1;

select user_id, max(streak) from (
  SELECT user_id, streak,
    case when @user_id is null OR @user_id != user_id then @streak := 1 else @streak := @streak + 1 end as streak_formula,
    @user_id := user_id,
    @streak as streak
  FROM my_table
) foo
group by user_id

Answer 2

Not sure if you've managed to get the other query to work but here's my attempt, definetly working - Sqlfiddle to prove it.

set @x=null;
set @y=0;

select sub.user_id as user_id,max(sub.streak) as streak
from
(
select 
case when @x is null then @x:=user_id end,
case 
when win=1 and @x=user_id then @y:=@y+1 
when win=0 and @x=user_id then @y:=0 
when win=1 and @x<>user_id then @y:=1
when win=0 and @x<>user_id then @y:=0
end as streak,
@x:=user_id as user_id
from your_table
) as sub
group by sub.user_id

How to get it to work on a PHP page and testing to see you're getting the right results is underneath, I have also optimized the query a bit:

mysql_query("set @y=0");
$query=mysql_query("select sub.user_id as user_id,max(sub.streak) as streak
from
(
select
case 
when win=1 and @x=user_id then @y:=@y+1 
when win=0 and @x=user_id then @y:=0 
when win=1 and @x<>user_id then @y:=1
when win=0 and @x<>user_id then @y:=0
end as streak,
@x:=user_id as user_id
from your_table
) as sub
group by sub.user_id");
while($row=mysql_fetch_assoc($query)){
print_r($row);}