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Mysql Alter Column Size
Posted on: January 13, 2009 at 12:00 AM

Mysql Alter Column Size is used to change the data size of a column in a table.

Mysql Alter Column Size

Mysql Alter Column Size is used to change the data size of a column in a table.

Understand with Example

The Tutorial illustrate an example from 'Mysql Alter Column Size'. To understand example we create table 'employees' that include empid as primary key.

Query to create table:-

CREATE TABLE `employees` (
            ->Empid int(10),  
            ->Empname varchar(60),
             ->date date
            ->PRIMARY KEY(empid)  
           ->);

Query to insert data into Table named employees:

The insert into add 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 employee1 values(02,'Komal','2008-12-23');
Query OK, 1 row affected (0.02 sec)

Query to view data of Table named employees:

To view the detail from table 'employee' we use select Query that return the records from table 'employees'.

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)

Data type of Table named employees before altering column size:

The Query below define the table field ,data type,Null ,key ,default etc properties.

+---------+-------------+------+-----+---------+----------------+
| 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)

Query to alter column size of the Table named employees:

The Query Alter is used to modify the definition of table 'employees' and change the size of column datatype.

mysql> alter table employees
    -> change empname empname varchar(130);
Query OK, 2 rows affected (0.13 sec)
Records: 2  Duplicates: 0  Warnings: 0

Data type of Table named employees after altering column size:-

mysql> describe employees;
+---------+--------------+------+-----+---------+----------------+
| Field   | Type         | Null | Key | Default | Extra          |
+---------+--------------+------+-----+---------+----------------+
| empid   | int(11)      | NO   | PRI | NULL    | auto_increment |
| empname | varchar(130) | YES  |     | NULL    |                |
| date    | date         | YES  |     | NULL    |                |
+---------+--------------+------+-----+---------+----------------+
3 rows in set (0.03 sec)

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