group and limited view

DROP TABLE IF EXISTS t_barang;
CREATE TABLE t_barang(
id INT AUTO_INCREMENT PRIMARY KEY,
nama VARCHAR(50),
kategori TINYINT,
jml TINYINT,
waktu DATE
);

INSERT INTO t_barang(nama,kategori,jml,waktu)
VALUES
('sepatu bot anak',1,6,'2017-04-01'),
('baju anak perempuan',2,4,'2017-04-01'),
('sepatu olahraga',1,8,'2017-04-01'),
('baju anak laki-laki',2,4,'2017-04-02'),
('sepatu bot dewasa',1,6,'2017-04-02'),
('sepatu olahraga anak',1,2,'2017-04-02'),
('sepatu futsal',1,9,'2017-04-03'),
('sepatu tenis',1,3,'2017-04-04'),
('sepatu golf',1,2,'2017-04-04'),
('baju tidur anak',2,4,'2017-04-05'),
('baju olahraga anak',2,5,'2017-04-06');

SELECT * FROM t_barang ORDER BY kategori,waktu DESC;

+----+----------------------+----------+------+------------+
| id | nama                 | kategori | jml  | waktu      |
+----+----------------------+----------+------+------------+
|  9 | sepatu golf          |        1 |    2 | 2017-04-04 |
|  8 | sepatu tenis         |        1 |    3 | 2017-04-04 |
|  7 | sepatu futsal        |        1 |    9 | 2017-04-03 |
|  6 | sepatu olahraga anak |        1 |    2 | 2017-04-02 |
|  5 | sepatu bot dewasa    |        1 |    6 | 2017-04-02 |
|  1 | sepatu bot anak      |        1 |    6 | 2017-04-01 |
|  3 | sepatu olahraga      |        1 |    8 | 2017-04-01 |
| 11 | baju olahraga anak   |        2 |    5 | 2017-04-06 |
| 10 | baju tidur anak      |        2 |    4 | 2017-04-05 |
|  4 | baju anak laki-laki  |        2 |    4 | 2017-04-02 |
|  2 | baju anak perempuan  |        2 |    4 | 2017-04-01 |
+----+----------------------+----------+------+------------+

SELECT a.nama,a.kategori, a.jml, DATE_FORMAT(a.waktu,'%d-%b-%Y') AS waktu
FROM (
  SELECT
    *,
    IF( @prev <> kategori, @rownum := 1, @rownum := @rownum+1 ) AS rank,
    @prev := kategori
  FROM t_barang t
  JOIN (SELECT @rownum := NULL, @prev := 0) AS r
  ORDER BY t.kategori,t.waktu DESC
) AS a
WHERE a.rank <= 3
ORDER BY kategori, waktu DESC;

+---------------------+----------+------+-------------+
| nama                | kategori | jml  | waktu       |
+---------------------+----------+------+-------------+
| sepatu tenis        |        1 |    3 | 04-Apr-2017 |
| sepatu golf         |        1 |    2 | 04-Apr-2017 |
| sepatu futsal       |        1 |    9 | 03-Apr-2017 |
| baju olahraga anak  |        2 |    5 | 06-Apr-2017 |
| baju tidur anak     |        2 |    4 | 05-Apr-2017 |
| baju anak laki-laki |        2 |    4 | 02-Apr-2017 |
+---------------------+----------+------+-------------+