MariaDB 10.3

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CREATE TABLE bsn_kode_agent(
   kodeagent VARCHAR(10) NOT NULL PRIMARY KEY
  ,fungsi    VARCHAR(40) NOT NULL
);
INSERT INTO bsn_kode_agent(kodeagent,fungsi) 
  VALUES
  ('a','sales agent')
, ('b','sales agent');
CREATE TABLE bsn_data(
   kodeagent   VARCHAR(1) NOT NULL
  ,kodeupline2 VARCHAR(2) NOT NULL
  ,periode     DATE  NOT NULL
);
INSERT INTO bsn_data(kodeagent,kodeupline2,periode) 
VALUES 
  ('a','b1','2018-12-01')
, ('a','b1','2018-12-01')
, ('a','b1','2018-12-01')
, ('a','c1','2018-12-01')
, ('a','c1','2018-12-01')
, ('a','c1','2018-12-01')
, ('a','d1','2018-12-01')
, ('a','d1','2018-12-01')
, ('a','e1','2018-12-01')
, ('a','f1','2018-12-01')
;
SELECT
    b.kodeagent
  , IFNULL( SUM( d.total ), 0 )  AS totps
FROM bsn_kode_agent AS b
LEFT JOIN (
        SELECT
            tableb.kodeupline2
          , tableb.kodeagent
          , tableb.total
          , ROW_NUMBER() OVER (PARTITION BY tableb.kodeagent
                                 ORDER BY tableb.total DESC) as rn
        FROM (
            SELECT
                bsn_data.kodeupline2
              , bsn_data.kodeagent
              , COUNT( 1 ) total
            FROM bsn_data
            WHERE  bsn_data.periode >= '2018-12-01'
              AND  bsn_data.periode <  '2018-12-01' + INTERVAL 1 MONTH
            GROUP BY
                bsn_data.kodeupline2
              , bsn_data.kodeagent
        ) AS tableb
    ) d ON d.kodeagent = b.kodeagent and d.rn <=3 
WHERE b.fungsi = 'sales agent'
group by
    b.kodeagent
ORDER BY
    totps DESC
    


kodeagent
totps


a
8

b
0


         SELECT
            tableb.kodeupline2
          , tableb.kodeagent
          , tableb.total
          , ROW_NUMBER() OVER (PARTITION BY tableb.kodeagent
                                 ORDER BY tableb.total DESC) as rn
        FROM (
            SELECT
                bsn_data.kodeupline2
              , bsn_data.kodeagent
              , COUNT( 1 ) total
            FROM bsn_data
            WHERE  bsn_data.periode >= '2018-12-01'
              AND  bsn_data.periode <  '2018-12-01' + INTERVAL 1 MONTH
            GROUP BY
                bsn_data.kodeupline2
              , bsn_data.kodeagent
        ) AS tableb


kodeupline2
kodeagent
total
rn


b1
a
3
1

c1
a
3
2

d1
a
2
3

e1
a
1
4

f1
a
1
5