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Categories / MySQL / Select Clause

 

Use COUNT and GROUP

/* mysql> select * from Item; +----+-----------+---------+---------+----------+------------+----------+---------------------+ | ID | Name      | InStock | OnOrder | Reserved | Department | Category | RowUpdate           | +----+-----------+---------+---------+----------+------------+----------+---------------------+ |  1 | Bloodshot |      10 |       5 |        1 | Popular    | Rock     | 2005-10-09 09:19:44 | |  2 | Most      |      10 |       5 |        2 | Classical  | Opera    | 2005-10-09 09:19:44 | |  3 | Jazz      |      17 |       4 |        3 | Popular    | Jazz     | 2005-10-09 09:19:44 | |  4 | Class     |       9 |       4 |        4 | Classical  | Dance    | 2005-10-09 09:19:44 | |  5 | Violin    |      24 |       2 |        5 | Classical  | General  | 2005-10-09 09:19:44 | |  6 | Cha Cha   |      16 |       6 |        6 | Classical  | Vocal    | 2005-10-09 09:19:44 | |  7 | Blues     |       2 |      25 |        7 | Popular    | Blues    | 2005-10-09 09:19:44 | |  8 | Pure      |      32 |       3 |       18 | Popular    | Jazz     | 2005-10-09 09:19:44 | |  9 | Mud       |      12 |      15 |       19 | Popular    | Country  | 2005-10-09 09:19:44 | | 10 | The       |       5 |      20 |       11 | Popular    | New Age  | 2005-10-09 09:19:44 | | 11 | Embrace   |      24 |      11 |       12 | Popular    | New Age  | 2005-10-09 09:19:44 | | 12 | Magic     |      42 |      17 |       13 | Classical  | General  | 2005-10-09 09:19:44 | | 13 | Lake      |      25 |      44 |       24 | Classical  | Dance    | 2005-10-09 09:19:44 | | 14 | LaLala    |      20 |      10 |        5 | Classical  | Opera    | 2005-10-09 09:19:44 | | 15 | Soul      |      15 |      30 |       16 | Popular    | Blues    | 2005-10-09 09:19:44 | | 16 | Stages    |      42 |       0 |        7 | Popular    | Blues    | 2005-10-09 09:19:44 | | 17 | Six       |      16 |       8 |        6 | Classical  | General  | 2005-10-09 09:19:44 | +----+-----------+---------+---------+----------+------------+----------+---------------------+ 17 rows in set (0.03 sec) mysql> SELECT Category, COUNT(*) AS Total     -> FROM Item     -> WHERE Department='Popular'     -> GROUP BY Category; +----------+-------+ | Category | Total | +----------+-------+ | Blues    |     3 | | Country  |     1 | | Jazz     |     2 | | New Age  |     2 | | Rock     |     1 | +----------+-------+ 5 rows in set (0.02 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;