AUTO_INCREMENT
Spiegazione
L'attributo AUTO_INCREMENT è utile per generare un'identità univoca per le righe.
Esempi
CREATE TABLE animali ( id MEDIUMINT NOT NULL AUTO_INCREMENT, nome CHAR(30) NOT NULL, PRIMARY KEY (id) ); INSERT INTO animals (nome) VALUES ('cane'),('gatto'),('pinguino'), ('volpe'),('balena'),('ostrica');
MariaDB [test]> SELECT * FROM animali; +----+----------+ | id | nome | +----+----------+ | 1 | cane | | 2 | gatto | | 3 | pinguino | | 4 | volpe | | 5 | balena | | 6 | ostrica | +----+----------+
Impostare il valore auto_increment:
MariaDB [test]> ALTER TABLE animals AUTO_INCREMENT=8;
MariaDB [test]> INSERT INTO animals (name) VALUES ('aardvark');
MariaDB [test]> SELECT * FROM animals;
+----+-----------+
| id | name |
+----+-----------+
| 1 | dog |
| 2 | cat |
| 3 | penguin |
| 4 | fox |
| 5 | whale |
| 6 | ostrich |
| 8 | aardvark |
+----+-----------+
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