Mysql Alter Autoincrement
Mysql Alter Autoincrement is used to modify the definition of existing
table and add autoincrement feature property to the primary key of existing
table. The Autoincrement feature allows you to generate a unique value by
incrementing the last number of the table and will automatically added
incremented to the table.
Understand with Example
The Tutorial illustrate an example from 'Mysql Alter Autoincrement'. To
understand this example we create a table 'employees' with field attribute and
datatype respectively.
Query to create table:-
CREATE TABLE `employees` (
->Empid int(10),
->Empname varchar(60),
->date date
->);
|
Query to insert data into Table named employees:
To insert the records or rows into a table employees we use insert into that
adds the records or rows to the table 'employees'.
mysql>insert into employees values(01,'Girish','2008-12-22');
Query OK, 1 row affected (0.02 sec)
mysql>insert into employees values(02,'Komal','2008-12-23');
Query OK, 1 row affected (0.02 sec)
|
Query to view data of Table named employees:
The select Query return the details of table employee1.
mysql> select * from employees;
|
Output:-
+-------+---------+------------+
| Empid | Empname | date |
+-------+---------+------------+
| 1 | Girish | 2008-12-22 |
| 2 | Komal | 2008-12-23 |
+-------+---------+------------+
2 rows in set (0.00 sec)
|
Query to view data type of Table named employees:
The Query below is used to describe the table properties field , Type,
Null , Key ,Extra , etc.
+---------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+-------+
| Empid | int(10) | NO | | 0 | |
| Empname | varchar(60) | NO | | | |
| date | date | YES | | NULL | |
+---------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
|
Query to alter auto increment to the primary key of the Table named
employees:
The Alter Query below is used to modify table 'employees' definition
and add autoincrement to the primary key of the table 'employees'. The
autoincrement allows you to generate a automatic unique value that add the
values to the records.
mysql> alter table employees
-> change Empid empid int auto_increment primary key;
Query OK, 2 rows affected (0.13 sec)
Records: 2 Duplicates: 0 Warnings: 0
|
Data type of Table named employees after adding auto increment feature to
the primary key:
mysql> describe employees;
+---------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+----------------+
| empid | int(11) | NO | PRI | NULL | auto_increment |
| Empname | varchar(60) | NO | | | |
| date | date | YES | | NULL | |
+---------+-------------+------+-----+---------+----------------+
3 rows in set (0.02 sec)
|
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