Add a WHERE clause that looks for NULL values in the book column that is named in the ON clause : Where « Where Clause « SQL / MySQL






  1. SQL / MySQL
  2. Where Clause
  3. Where

Add a WHERE clause that looks for NULL values in the book column that is named in the ON clause

       
mysql>
mysql> CREATE TABLE author
    -> (
    ->     a_id INT UNSIGNED NOT NULL AUTO_INCREMENT, # author ID
    ->     name VARCHAR(30) NOT NULL, # author name
    ->     PRIMARY KEY (a_id),
    ->     UNIQUE (name)
    -> );
Query OK, 0 rows affected (0.01 sec)

mysql> CREATE TABLE book
    -> (
    ->     a_id INT UNSIGNED NOT NULL, # author ID
    ->     p_id INT UNSIGNED NOT NULL AUTO_INCREMENT, # book ID
    ->     title VARCHAR(100) NOT NULL, # title of book
    ->     state VARCHAR(2) NOT NULL, # state where purchased
    ->     price INT UNSIGNED, # purchase price (dollars)
    ->     INDEX (a_id),
    ->     PRIMARY KEY (p_id)
    -> );
Query OK, 0 rows affected (0.01 sec)

mysql>
mysql> INSERT INTO author (name) VALUES
    ->  ('Tom'),
    ->  ('Monet'),
    ->  ('Jack'),
    ->  ('Picasso'),
    ->  ('Mary')
    -> ;
Query OK, 5 rows affected (0.00 sec)
Records: 5  Duplicates: 0  Warnings: 0

mysql>
mysql>
mysql>
mysql> INSERT INTO book (a_id,title,state,price)
    ->  SELECT a_id, 'Database', 'IN', 34 FROM author WHERE name = 'Tom';
Query OK, 1 row affected (0.00 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql>
mysql> INSERT INTO book (a_id,title,state,price)
    ->  SELECT a_id, 'SQL', 'MI', 87 FROM author WHERE name = 'Tom';
Query OK, 1 row affected (0.00 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql>
mysql> INSERT INTO book (a_id,title,state,price)
    ->  SELECT a_id, 'MySQL', 'KY', 48 FROM author WHERE name = 'Jack';
Query OK, 1 row affected (0.00 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> INSERT INTO book (a_id,title,state,price)
    ->  SELECT a_id, 'XML', 'KY', 67    FROM author WHERE name = 'Jack';
Query OK, 1 row affected (0.00 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> INSERT INTO book (a_id,title,state,price)
    ->  SELECT a_id, 'Java', 'IA', 33   FROM author WHERE name = 'Jack';
Query OK, 1 row affected (0.00 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql>
mysql> INSERT INTO book (a_id,title,state,price)
    ->  SELECT a_id, 'HTML', 'NE', 64   FROM author WHERE name = 'Mary';
Query OK, 1 row affected (0.00 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql>
mysql>
mysql>
mysql> SELECT * FROM author LEFT JOIN book
    -> ON author.a_id = book.a_id
    -> WHERE book.a_id IS NULL;
+------+---------+------+------+-------+-------+-------+
| a_id | name    | a_id | p_id | title | state | price |
+------+---------+------+------+-------+-------+-------+
|    2 | Monet   | NULL | NULL | NULL  | NULL  |  NULL |
|    4 | Picasso | NULL | NULL | NULL  | NULL  |  NULL |
+------+---------+------+------+-------+-------+-------+
2 rows in set (0.00 sec)

mysql>
mysql> drop table book;
Query OK, 0 rows affected (0.00 sec)

mysql> drop table author;
Query OK, 0 rows affected (0.00 sec)








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