Mysql-将变量从子句传递给子查询

Question

I have the following query that I am working on, you'll find sample data on this db fiddle :

SET @count=0; 
SELECT ( @rank := IF(@points = points, @rank + 1, IF(@points := points, @rank + 1, @rank + 1)) ) AS rank,
       er.* 
FROM (SELECT cc6_MensLeague_players.id AS `id`, 
             ( 1288 ) AS points, 
             (SELECT Max(@count := IF(outcome = 2, @count + 1, 0)) AS max_consecutive_wins 
              FROM (SELECT * 
                    FROM cc6_MensLeague_rounds 
                    WHERE player = 785 
                    ORDER BY date ASC) AS temp
              ) AS `maxcon` 
      FROM cc6_MensLeague_players 
      GROUP BY `id`) er 
CROSS JOIN (SELECT @rank := 0, @points := -1) params 
ORDER BY id DESC; 

This code works perfect (thanks to Tobias Thornfeldt Nissen) but what I'm now trying to do is make the player id (785) dynamic... I can't seem to pass my id variable (cc6_MensLeague_players.id) to the subquery from clause.

I have tried the following methods:

1. Adding @id := to the beginning of ... cc6_mensleague_players.id AS id ... and changing ... WHERE player = 785 ... to ... WHERE player = @id ... NO LUCK!

2. Changing ... player = 785 ORDER BY DATE ASC ... to ... player = @id GROUP BY ID ORDER BY DATE ASC ... NO LUCK!

3. I have also tried a few other tactics but I just can't figure it out.

So my question is: How do I make WHERE player = cc6_mensleague_players.id (line 9) work?

If you can point me in the right direction it would be greatly appreciated.

Thanks.

Answer 1

you can use the alias that you gave to the subquery as id :

SET @count=0;

SELECT ( @rank := IF(@points = points, @rank + 1,
                  IF(
                  @points := points,
                           @rank + 1,
                                    @rank + 1)) )
       AS rank,
       er.*
FROM   (SELECT cc6_MensLeague_players.id
               AS
                      `id`,
               ( 1288 )
               AS
                      points,
               (SELECT Max(@count := IF(
                           outcome = 2,
                                     @count + 1,
                                     0)) AS
                       max_consecutive_wins
                FROM   (SELECT *
                        FROM
               cc6_MensLeague_rounds
                        WHERE  player = `id`
                        ORDER  BY date ASC) AS
                       temp) AS
                      `maxcon`
        FROM   cc6_MensLeague_players
        GROUP  BY `id`) er
       CROSS JOIN (SELECT @rank := 0,
                          @points := -1) params
ORDER  BY id DESC;

Answer 2

Thanks for your replies :-)

I was able to figure out the solution. Couldn't have done it without all of you.

I ended up removing the brackets surrounding the 2nd from clause

... FROM (SELECT * ... ) AS temp ...

and voila - The @id variable worked like a charm

Here is the final piece of code

set @id=0, @count=0; select ( @rank := if(@points = points, @rank + 1, if(@points := points, @rank + 1, @rank + 1)) ) as rank, er.* from (select @id := cc6_MensLeague_players.id as set @id=0, @count=0; select ( @rank := if(@points = points, @rank + 1, if(@points := points, @rank + 1, @rank + 1)) ) as rank, er.* from (select @id := cc6_MensLeague_players.id as id , ( 1288 ) as points, (select max(@count := if(outcome = 2, @count + 1, 0)) as MaxWins from cc6_MensLeague_rounds where player = @id order by date asc ) as maxcon from cc6_MensLeague_players group by id ) er cross join (select @rank := 0, @points := -1) params order by id desc;

https://www.db-fiddle.com/f/35EQE2yzdxNs3KHZnQkMuQ/6

Thanks Everyone.