Alter table: add unique : Unique « Select Clause « SQL / MySQL

1. SQL / MySQL
2. Select Clause
3. Unique

Alter table: add unique

/*
mysql> Drop table Product;

mysql> CREATE TABLE Product
    -> (
    ->    ID SMALLINT UNSIGNED NOT NULL PRIMARY KEY,
    ->    ModelID SMALLINT UNSIGNED NOT NULL
    -> );
Query OK, 0 rows affected (0.05 sec)

mysql> ALTER TABLE Product
    -> ADD UNIQUE (ID, ModelID);
Query OK, 0 rows affected (0.15 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> Describe Product;
+---------+----------------------+------+-----+---------+-------+
| Field   | Type                 | Null | Key | Default | Extra |
+---------+----------------------+------+-----+---------+-------+
| ID      | smallint(5) unsigned |      | PRI | 0       |       |
| ModelID | smallint(5) unsigned |      |     | 0       |       |
+---------+----------------------+------+-----+---------+-------+
2 rows in set (0.01 sec)


*/

Drop table Product;


CREATE TABLE Product
(
   ID SMALLINT UNSIGNED NOT NULL PRIMARY KEY,
   ModelID SMALLINT UNSIGNED NOT NULL
);

ALTER TABLE Product
ADD UNIQUE (ID, ModelID);

Describe Product;

           
       

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