MySQL top-N ranking and sum the rest of same group

问题

I've researched most of the time with this topic, however I couldn't get a efficient and perfect answer regarding ranking (top 3) a MySQL table with group and aggregate using sum() to the rest.

The data are as following:

TS         | Name     | Count
=============================
1552286160 | Apple    | 7
1552286160 | Orange   | 8
1552286160 | Grape    | 8
1552286160 | Pear     | 9
1552286160 | Kiwi     | 10
...
1552286100 | Apple    | 10
1552286100 | Orange   | 12
1552286100 | Grape    | 14
1552286100 | Pear     | 16
1552286100 | Kiwi     | 9
...
1552286040 | Apple    | 4
1552286040 | Orange   | 2
1552286040 | Grape    | 3
1552286040 | Pear     | 7
1552286040 | Kiwi     | 9
...

With this dataset, I would like to form Top 3 by each TS group, and 1 row with sum(Count) of the rest that group, like following:

TS         | Name     | Count
=============================
1552286160 | Kiwi     | 10
1552286160 | Pear     | 9
1552286160 | Grape    | 8
1552286160 | Other    | 8 + 7
...
1552286100 | Pear     | 16
1552286100 | Grape    | 14
1552286100 | Orange   | 12
1552286100 | Other    | 10 + 9
...
1552286040 | Kiwi     | 9
1552286040 | Pear     | 7
1552286040 | Apple    | 4
1552286040 | Other    | 3 + 2
...

The closest hint is actually provided via http://www.silota.com/docs/recipes/sql-top-n-aggregate-rest-other.html However, the solution was just for a single group.

The SQL Fiddle that I've prepared is located here: http://sqlfiddle.com/#!9/3cedd0/10

Appreciate if there's any solutions.

回答1:

DROP TABLE IF EXISTS my_table;

CREATE TABLE my_table
(ts INT NOT NULL
,name VARCHAR(12) NOT NULL
,count INT NOT NULL
,PRIMARY KEY(ts,name)
);

INSERT INTO my_table VALUES
(1552286160,'Apple' , 7),
(1552286160,'Orange', 8),
(1552286160,'Grape' , 8),
(1552286160,'Pear'  , 9),
(1552286160,'Kiwi'  ,10),
(1552286100,'Apple' ,10),
(1552286100,'Orange',12),
(1552286100,'Grape' ,14),
(1552286100,'Pear'  ,16),
(1552286100,'Kiwi'  , 9),
(1552286040,'Apple' , 4),
(1552286040,'Orange', 2),
(1552286040,'Grape' , 3),
(1552286040,'Pear'  , 7),
(1552286040,'Kiwi'  , 9);

SELECT ts
     , CASE WHEN i>3 THEN 'other' ELSE name END name
     , SUM(count) count
  FROM 
     ( SELECT x.*
            , CASE WHEN @prev=ts THEN @i:=@i+1 ELSE @i:=1 END i
            , @prev:=ts 
         FROM my_table x
            , (SELECT @prev:=null,@i:=0) vars 
        ORDER 
           BY ts
            , count DESC
            , name
     ) a
 GROUP
    BY ts
     , CASE WHEN i>3 THEN 'other' ELSE name END;

+------------+--------+-------+
| ts         | name   | count |
+------------+--------+-------+
| 1552286040 | Apple  |     4 |
| 1552286040 | Kiwi   |     9 |
| 1552286040 | other  |     5 |
| 1552286040 | Pear   |     7 |
| 1552286100 | Grape  |    14 |
| 1552286100 | Orange |    12 |
| 1552286100 | other  |    19 |
| 1552286100 | Pear   |    16 |
| 1552286160 | Grape  |     8 |
| 1552286160 | Kiwi   |    10 |
| 1552286160 | other  |    15 |
| 1552286160 | Pear   |     9 |
+------------+--------+-------+

来源：https://stackoverflow.com/questions/55098157/mysql-top-n-ranking-and-sum-the-rest-of-same-group

标签

mysql

sum

aggregate

top-n