Alter table to drop primary key and foreign key : Foreign Keys « Table « MySQL Tutorial

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MySQL Tutorial » Table » Foreign Keys 
4. 16. 5. Alter table to drop primary key and foreign key
mysql>
mysql>
mysql> CREATE TABLE Publishers
    -> (
    ->    PubID SMALLINT NOT NULL DEFAULT 1
    -> )
    -> ENGINE=INNODB;
Query OK, rows affected (0.08 sec)

mysql>
mysql>
mysql> CREATE TABLE Books
    -> (
    ->    BookID SMALLINT NOT NULL,
    ->    BookName VARCHAR(40NOT NULL,
    ->    PubID SMALLINT NOT NULL DEFAULT 1
    -> )
    -> ENGINE=INNODB;
Query OK, rows affected (0.06 sec)

mysql>
mysql>
mysql> ALTER TABLE Books
    -> ADD PRIMARY KEY (BookID),
    -> ADD CONSTRAINT fk_1 FOREIGN KEY (PubIDREFERENCES Publishers (PubID),
    -> ADD COLUMN Format ENUM('paperback', 'hardcover') NOT NULL AFTER BookName;
ERROR 1005 (HY000): Can't create table '.\test\#sql-a98_3a.frm' (errno: 150)
mysql>
mysql> desc Books;
+----------+-------------+------+-----+---------+-------+
| Field    | Type        | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| BookID   | smallint(6| NO   |     |         |       |
| BookName | varchar(40| NO   |     |         |       |
| PubID    | smallint(6| NO   |     | 1       |       |
+----------+-------------+------+-----+---------+-------+
rows in set (0.00 sec)

mysql>
mysql> desc Publishers;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| PubID | smallint(6| NO   |     | 1       |       |
+-------+-------------+------+-----+---------+-------+
row in set (0.01 sec)

mysql>
mysql>
mysql>
mysql> ALTER TABLE Books
    -> DROP PRIMARY KEY,
    -> DROP FOREIGN KEY fk_1,
    -> DROP COLUMN Format;
ERROR 1091 (42000): Can't DROP 'PRIMARY'; check that column/key exists
mysql>
mysql>
mysql> desc Books;
+----------+-------------+------+-----+---------+-------+
| Field    | Type        | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| BookID   | smallint(6| NO   |     |         |       |
| BookName | varchar(40| NO   |     |         |       |
| PubID    | smallint(6| NO   |     | 1       |       |
+----------+-------------+------+-----+---------+-------+
rows in set (0.00 sec)

mysql>
mysql> desc Publishers;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| PubID | smallint(6| NO   |     | 1       |       |
+-------+-------------+------+-----+---------+-------+
row in set (0.01 sec)

mysql>
mysql> drop table Books;
Query OK, rows affected (0.03 sec)

mysql>
mysql> drop table Publishers;
Query OK, rows affected (0.03 sec)
4. 16. Foreign Keys
4. 16. 1. Using Foreign Keys
4. 16. 2. Using AUTO_INCREMENT
4. 16. 3. Implement a many-to-many map
4. 16. 4. One table with two foreign keys
4. 16. 5. Alter table to drop primary key and foreign key
4. 16. 6. Add Index and primary key to a table in table creation command
4. 16. 7. FOREIGN KEY ON DELETE CASCADE ON UPDATE CASCADE
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