MySQL Automatic ID column - mysql

Question

I was wondering how to make MySQL automatically have a column that adds 1 to every row that is made (Row 1 will have ID 1, Row 2 will get ID 2, etc.)
For example:
Every time a new user signs up on a website, they are assigned an ID number. Starting at 1, then 2, etc.
ID|Username|Password
1 |Bob |drowssaP
2 |Jill |cats

Answer 1

Try AUTO_INCREMENT. Documentation here
If you add, that magic word :) to your table creation declaration, it will do the magic for you :)
mysql> CREATE TABLE Users (
-> ID int NOT NULL AUTO_INCREMENT PRIMARY KEY,
-> Username varchar(255) NOT NULL,
-> Password varchar(255) NOT NULL
-> );
Query OK, 0 rows affected (0.52 sec)
mysql> INSERT INTO Users(Username, Password) VALUES('vladimir', 'ilich_lenin');
Query OK, 1 row affected (0.12 sec)
mysql> INSERT INTO Users(Username, Password) VALUES('friedrich', 'engels');
Query OK, 1 row affected (0.04 sec)
mysql> SELECT * FROM Users;
+----+-----------+-------------+
| ID | Username | Password |
+----+-----------+-------------+
| 1 | vladimir | ilich_lenin |
| 2 | friedrich | engels |
+----+-----------+-------------+
2 rows in set (0.02 sec)
EDIT
mysql> CREATE TABLE Persons ( ID int NOT NULL PRIMARY KEY, Username varchar(255) NOT NULL, Password varchar(255) NOT NULL);
Query OK, 0 rows affected (0.25 sec)
mysql> SHOW CREATE TABLE
CREATE TABLE `Persons` (
`ID` int(11) NOT NULL,
`Username` varchar(255) NOT NULL,
`Password` varchar(255) NOT NULL,
PRIMARY KEY (`ID`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
1 row in set (0.00 sec)
mysql> ALTER TABLE Persons MODIFY ID INTEGER NOT NULL AUTO_INCREMENT;
Query OK, 0 rows affected (0.50 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> SHOW CREATE TABLE Persons;
CREATE TABLE `Persons` (
`ID` int(11) NOT NULL AUTO_INCREMENT,
`Username` varchar(255) NOT NULL,
`Password` varchar(255) NOT NULL,
PRIMARY KEY (`ID`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
1 row in set (0.00 sec)
mysql> INSERT INTO Persons(Username, Password) VALUES('friedrich', 'engels');
Query OK, 1 row affected (0.06 sec)
mysql> INSERT INTO Persons(Username, Password) VALUES('karl', 'marx');
Query OK, 1 row affected (0.08 sec)
mysql> SELECT * FROM Persons
-> ;
+----+-----------+----------+
| ID | Username | Password |
+----+-----------+----------+
| 1 | friedrich | engels |
| 2 | karl | marx |
+----+-----------+----------+
2 rows in set (0.00 sec)