Use COUNT, GROUP and HAVING : Count « Select Clause « SQL / MySQL






Use COUNT, GROUP and HAVING

/*

mysql> select * from Item;
+----+-----------+---------+---------+----------+------------+----------+---------------------+
| ID | Name      | InStock | OnOrder | Reserved | Department | Category | RowUpdate           |
+----+-----------+---------+---------+----------+------------+----------+---------------------+
|  1 | Bloodshot |      10 |       5 |        1 | Popular    | Rock     | 2005-10-09 09:19:45 |
|  2 | Most      |      10 |       5 |        2 | Classical  | Opera    | 2005-10-09 09:19:45 |
|  3 | Jazz      |      17 |       4 |        3 | Popular    | Jazz     | 2005-10-09 09:19:45 |
|  4 | Class     |       9 |       4 |        4 | Classical  | Dance    | 2005-10-09 09:19:45 |
|  5 | Violin    |      24 |       2 |        5 | Classical  | General  | 2005-10-09 09:19:45 |
|  6 | Cha Cha   |      16 |       6 |        6 | Classical  | Vocal    | 2005-10-09 09:19:45 |
|  7 | Blues     |       2 |      25 |        7 | Popular    | Blues    | 2005-10-09 09:19:45 |
|  8 | Pure      |      32 |       3 |       18 | Popular    | Jazz     | 2005-10-09 09:19:45 |
|  9 | Mud       |      12 |      15 |       19 | Popular    | Country  | 2005-10-09 09:19:45 |
| 10 | The       |       5 |      20 |       11 | Popular    | New Age  | 2005-10-09 09:19:45 |
| 11 | Embrace   |      24 |      11 |       12 | Popular    | New Age  | 2005-10-09 09:19:45 |
| 12 | Magic     |      42 |      17 |       13 | Classical  | General  | 2005-10-09 09:19:45 |
| 13 | Lake      |      25 |      44 |       24 | Classical  | Dance    | 2005-10-09 09:19:45 |
| 14 | LaLala    |      20 |      10 |        5 | Classical  | Opera    | 2005-10-09 09:19:45 |
| 15 | Soul      |      15 |      30 |       16 | Popular    | Blues    | 2005-10-09 09:19:45 |
| 16 | Stages    |      42 |       0 |        7 | Popular    | Blues    | 2005-10-09 09:19:45 |
| 17 | Six       |      16 |       8 |        6 | Classical  | General  | 2005-10-09 09:19:45 |
+----+-----------+---------+---------+----------+------------+----------+---------------------+
17 rows in set (0.00 sec)

mysql> SELECT Category, COUNT(*) AS Total
    -> FROM Item
    -> WHERE Department='Popular'
    -> GROUP BY Category
    -> HAVING Total < 3;
+----------+-------+
| Category | Total |
+----------+-------+
| Country  |     1 |
| Jazz     |     2 |
| New Age  |     2 |
| Rock     |     1 |
+----------+-------+
4 rows in set (0.00 sec)

*/

Drop table Item;

CREATE TABLE Item
(
   ID SMALLINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
   Name VARCHAR(50) NOT NULL,
   InStock SMALLINT UNSIGNED NOT NULL,
   OnOrder SMALLINT UNSIGNED NOT NULL,
   Reserved SMALLINT UNSIGNED NOT NULL,
   Department ENUM('Classical', 'Popular') NOT NULL,
   Category VARCHAR(20) NOT NULL,
   RowUpdate TIMESTAMP NOT NULL
);


INSERT INTO Item (Name, InStock, OnOrder, Reserved, Department, Category)
          VALUES ('Bloodshot',      10,      5,       1, 'Popular',      'Rock'),
                 ('Most',           10,      5,       2, 'Classical',    'Opera'),
                 ('Jazz',           17,      4,       3, 'Popular',      'Jazz'),
                 ('Class',           9,      4,       4, 'Classical',    'Dance'),
                 ('Violin',         24,      2,       5, 'Classical',    'General'),
                 ('Cha Cha',        16,      6,       6, 'Classical',    'Vocal'),
                 ('Blues',           2,     25,       7, 'Popular',      'Blues'),
                 ('Pure',           32,      3,      18, 'Popular',      'Jazz'),
                 ('Mud',            12,     15,      19, 'Popular',      'Country'),
                 ('The',             5,     20,      11, 'Popular',      'New Age'),
                 ('Embrace',        24,     11,      12, 'Popular',      'New Age'),
                 ('Magic',          42,     17,      13, 'Classical',    'General'),
                 ('Lake',           25,     44,      24, 'Classical',    'Dance'),
                 ('LaLala',         20,     10,       5, 'Classical',    'Opera'),
                 ('Soul',           15,     30,      16, 'Popular',      'Blues'),
                 ('Stages',         42,      0,       7, 'Popular',      'Blues'),
                 ('Six',            16,      8,       6, 'Classical',    'General');

select * from Item;

SELECT Category, COUNT(*) AS Total
FROM Item
WHERE Department='Popular'
GROUP BY Category
HAVING Total < 3;



           
       








Related examples in the same category

1.Counting Rows: Counting the total number of animals
2.Count and group
3.Use COUNT in select command
4.COUNT() and GROUP BY
5.Another Count and Group BY
6.Count and group by two columns
7.COUNT command with condition
8.COUNT with condition and group
9.Get GROUP BY for COUNT
10.Use COUNT with condition
11.Simple COUNT
12.Performing Row and Column Counting
13.Use COUNT and GROUP