mySQL “get TOP 100 scores” query is turning me crazy

问题

I have asked this question Friday and since then I have been trying everything I could think of with no success

I cannot get this to work

SELECT * FROM WorldFlowers_table GROUP BY device_id ORDER BY score DESC LIMIT 100

and return me :

the 100 rows with the top 100 scores
filtered so that only the highest score of each device_id is featured
ORDER BY score DESC

@ 1000111 and Giorgos Betsos

A guy comes into a room, says, "please help, I'm getting crazy trying with all my forces to solve a simple problem that any of you could solve in the blink of an eye"

2 guys turn around, shoot the guy in the face and say "duplicate"

I am getting exhausted :(

///////// to adress Strawberry comment

I tried building that in SQLFiddle

CREATE TABLE WorldFlowers_table 
    (
     id int identity primary key, 
     timestamp varchar(20), 
     name varchar(30),
     score int,
     color varchar(30),
     flower varchar(30),
     device_id varchar(30),
    );

INSERT INTO WorldFlowers_table
(timestamp, name,score, color, flower, device_id  )
VALUES
('1475151826', 'RI-RI', 42, '0|0|0|0|0|0|0|0|0|0', '[1475152768|42|4|0.0]', 'XYZ' ),
('1475151826', 'RO-RO', 46, '0|0|0|0|0|0|0|0|0|0', '[1475152768|42|4|0.0]', 'ABC' ),
('1475151826', 'RI-RI', 42, '0|0|0|0|0|0|0|0|0|0', '[1475152768|42|4|0.0]', 'XYZ' ),
('1475151826', 'RA-RA', 45, '0|0|0|0|0|0|0|0|0|0', '[1475152768|42|4|0.0]', 'ABC' ),
('1475151826', 'RU-RU', 42, '0|0|0|0|0|0|0|0|0|0', '[1475152768|42|4|0.0]', 'XYZ' ),
('1475151826', 'RE-RE', 44, '0|0|0|0|0|0|0|0|0|0', '[1475152768|42|4|0.0]', 'DEF' ),
('1475151826', 'RY-RY', 42, '0|0|0|0|0|0|0|0|0|0', '[1475152768|42|4|0.0]', 'XYZ' ),
('1475151826', 'RX-RX', 43, '0|0|0|0|0|0|0|0|0|0', '[1475152768|42|4|0.0]', 'XYZ' ),
('1475151826', 'RA-RA', 42, '0|0|0|0|0|0|0|0|0|0', '[1475152768|42|4|0.0]', 'DEF' );

but is does only builds one time out of 2.

The return I am looking for would then be

+------+------------+--------------------------------------------+
| id   | timestamp  | name  | score | color | flower | device_id |                               
+------+------------+--------------------------------------------+
| 2    | blabla     | RO-RO |  46   |  ...  |   ...  |   ABC     | 
| 5    | blabla     | RE-RE |  44   |  ...  |   ...  |   DEF     |
| 7    | blabla     | RX-RX |  43   |  ...  |   ...  |   XYZ     |
+------+-------+-------------------------------------------------+

. only 1 of each device-id per return

. the highest score per device-id

. and the result being given in ORDER BY score DESC

UPDATE: this from scaisEdge seems to work fine

SELECT * FROM scores WHERE (name, score) IN ( SELECT name, MAX(score) FROM scores GROUP BY name
ORDER BY score DESC ) ORDER BY score DESC LIMIT 100 ;

回答1:

If i undestand right you want the top 100 highest device score

  SELECT *
  FROM WorldFlowers_table
  WHERE (device_id, score) IN (SELECT device_id, max(score) 
                               FROM WorldFlowers_table 
                               GROUP BY device_id )
  ORDER BY score DESC 
  LIMIT 100

回答2:

MySQL does not support LIMIT in subqueries for certain subquery operators:

mysql> SELECT * FROM t1
    ->   WHERE s1 IN (SELECT s2 FROM t2 ORDER BY s1 LIMIT 1);
ERROR 1235 (42000): This version of MySQL doesn't yet support
 'LIMIT & IN/ALL/ANY/SOME subquery'

https://dev.mysql.com/doc/mysql-reslimits-excerpt/5.6/en/subquery-restrictions.html

Take a look here:

Problem with LIMIT & IN/ALL/ANY/SOME subquery

回答3:

SELECT id, timestamp, name, score, color, flower, device_id
    FROM WorldFlowers_table 
    WHERE (device_id, score) IN 
    (SELECT device_id, MAX(score) FROM WorldFlowers_table GROUP BY device_id)
ORDER BY score DESC LIMIT 100;

来源：https://stackoverflow.com/questions/39833606/mysql-get-top-100-scores-query-is-turning-me-crazy

标签

mysql

greatest-n-per-group