mysql> CREATE TABLE IF NOT EXISTS dishes
-> (
-> id INT NOT NULL,
-> pattern VARCHAR(25) NOT NULL,
-> price DECIMAL(6,2)
-> );
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> EXPLAIN dishes; # confirm the "dishes" table format
+---------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+--------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| pattern | varchar(25) | NO | | NULL | |
| price | decimal(6,2) | YES | | NULL | |
+---------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
mysql>
mysql> ALTER TABLE dishes
-> ADD PRIMARY KEY(id),
-> ADD COLUMN code INT UNIQUE NOT NULL,
-> CHANGE pattern dish_pattern VARCHAR(25) NOT NULL,
-> DROP COLUMN price;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql>
mysql> EXPLAIN dishes; # confirm the "dishes" table format
+--------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+-------------+------+-----+---------+-------+
| id | int(11) | NO | PRI | NULL | |
| dish_pattern | varchar(25) | NO | | NULL | |
| code | int(11) | NO | UNI | NULL | |
+--------------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
mysql> DROP TABLE dishes; # delete this sample table
Query OK, 0 rows affected (0.00 sec)