The Ultimate Guide to High Availability with MariaDB

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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