Use NULL in where clause
/*
mysql> Drop table Sale;
mysql> CREATE TABLE Sale
-> (
-> 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)
-> );
Query OK, 0 rows affected (0.07 sec)
mysql> INSERT INTO Sale (Name, InStock, OnOrder, Reserved, Department, Cate
gory)
-> VALUES ('Bloodshot', 11, 6, 1, 'Popular', 'Ro
ck'),
-> ('Opera', 12, 5, 2, 'Classical','Op
era'),
-> ('Jazz', 13, 4, 3, 'Popular', 'Ja
zz'),
-> ('Music', 4, 3, 4, 'Classical','Da
nce'),
-> ('Violin', 25, 2, 5, 'Classical', NU
LL),
-> ('Toscana', 16, 1, 6, 'Classical', NU
LL),
-> ('Blues', 7, 22, 7, 'Popular', 'B
lues'),
-> ('Pure', 38, 5, 11, 'Popular', NU
LL),
-> ('Mud', 19, 11, 12, 'Popular', 'Co
untry'),
-> ('Essence', 5, 23, 12, 'Popular', 'New
Age'),
-> ('Embrace', 21, 12, 14, 'Popular', 'New
Age'),
-> ('Satie', 42, 17, 15, 'Classical', NU
LL),
-> ('Lake', 23, 47, 28, 'Classical', 'D
ance'),
-> ('Favorites', 34, 15, 12, 'Classical', 'G
eneral'),
-> ('Boheme', 25, 12, 5, 'Classical', 'O
pera'),
-> ('Cantatas', 26, 13, 8, 'Classical', 'G
eneral'),
-> ('Road', 27, 13, 17, 'Popular', 'Cou
ntry'),
-> ('Paris', 18, 25, 10, 'Popular', 'Jaz
z'),
-> ('Woman', 29, 4, 7, 'Popular', 'Blu
es'),
-> ('Bach', 21, 13, 16, 'Classical', 'G
eneral'),
-> ('Opera', 12, 32, 12, 'Classical', 'O
pera'),
-> ('Soul', 13, 30, 14, 'Popular', NULL
),
-> ('Stages', 44, 0, 8, 'Popular', 'Blu
es'),
-> ('Bach', 15, 1, 8, 'Classical', 'G
eneral');
Query OK, 24 rows affected (0.00 sec)
Records: 24 Duplicates: 0 Warnings: 0
mysql> select * from Sale;
+----+-----------+---------+---------+----------+------------+----------+
| ID | Name | InStock | OnOrder | Reserved | Department | Category |
+----+-----------+---------+---------+----------+------------+----------+
| 1 | Bloodshot | 11 | 6 | 1 | Popular | Rock |
| 2 | Opera | 12 | 5 | 2 | Classical | Opera |
| 3 | Jazz | 13 | 4 | 3 | Popular | Jazz |
| 4 | Music | 4 | 3 | 4 | Classical | Dance |
| 5 | Violin | 25 | 2 | 5 | Classical | NULL |
| 6 | Toscana | 16 | 1 | 6 | Classical | NULL |
| 7 | Blues | 7 | 22 | 7 | Popular | Blues |
| 8 | Pure | 38 | 5 | 11 | Popular | NULL |
| 9 | Mud | 19 | 11 | 12 | Popular | Country |
| 10 | Essence | 5 | 23 | 12 | Popular | New Age |
| 11 | Embrace | 21 | 12 | 14 | Popular | New Age |
| 12 | Satie | 42 | 17 | 15 | Classical | NULL |
| 13 | Lake | 23 | 47 | 28 | Classical | Dance |
| 14 | Favorites | 34 | 15 | 12 | Classical | General |
| 15 | Boheme | 25 | 12 | 5 | Classical | Opera |
| 16 | Cantatas | 26 | 13 | 8 | Classical | General |
| 17 | Road | 27 | 13 | 17 | Popular | Country |
| 18 | Paris | 18 | 25 | 10 | Popular | Jazz |
| 19 | Woman | 29 | 4 | 7 | Popular | Blues |
| 20 | Bach | 21 | 13 | 16 | Classical | General |
| 21 | Opera | 12 | 32 | 12 | Classical | Opera |
| 22 | Soul | 13 | 30 | 14 | Popular | NULL |
| 23 | Stages | 44 | 0 | 8 | Popular | Blues |
| 24 | Bach | 15 | 1 | 8 | Classical | General |
+----+-----------+---------+---------+----------+------------+----------+
24 rows in set (0.00 sec)
mysql> SELECT Name, Department, Category
-> FROM Sale
-> WHERE Category=NULL
-> ORDER BY Name;
Empty set (0.00 sec)
*/
Drop table Sale;
CREATE TABLE Sale
(
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)
);
INSERT INTO Sale (Name, InStock, OnOrder, Reserved, Department, Category)
VALUES ('Bloodshot', 11, 6, 1, 'Popular', 'Rock'),
('Opera', 12, 5, 2, 'Classical','Opera'),
('Jazz', 13, 4, 3, 'Popular', 'Jazz'),
('Music', 4, 3, 4, 'Classical','Dance'),
('Violin', 25, 2, 5, 'Classical', NULL),
('Toscana', 16, 1, 6, 'Classical', NULL),
('Blues', 7, 22, 7, 'Popular', 'Blues'),
('Pure', 38, 5, 11, 'Popular', NULL),
('Mud', 19, 11, 12, 'Popular', 'Country'),
('Essence', 5, 23, 12, 'Popular', 'New Age'),
('Embrace', 21, 12, 14, 'Popular', 'New Age'),
('Satie', 42, 17, 15, 'Classical', NULL),
('Lake', 23, 47, 28, 'Classical', 'Dance'),
('Favorites', 34, 15, 12, 'Classical', 'General'),
('Boheme', 25, 12, 5, 'Classical', 'Opera'),
('Cantatas', 26, 13, 8, 'Classical', 'General'),
('Road', 27, 13, 17, 'Popular', 'Country'),
('Paris', 18, 25, 10, 'Popular', 'Jazz'),
('Woman', 29, 4, 7, 'Popular', 'Blues'),
('Bach', 21, 13, 16, 'Classical', 'General'),
('Opera', 12, 32, 12, 'Classical', 'Opera'),
('Soul', 13, 30, 14, 'Popular', NULL),
('Stages', 44, 0, 8, 'Popular', 'Blues'),
('Bach', 15, 1, 8, 'Classical', 'General');
select * from Sale;
SELECT Name, Department, Category
FROM Sale
WHERE Category=NULL
ORDER BY Name;
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