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SQL Query to Alter Column Size in MySQL

  • Last Updated : 31 Aug, 2021
Geek Week

Sometimes you may need to change column size or change field length in MySQL. In this article, we will look at how to change column size in MySQL. You can use these commands to increase column size in MySQL or decrease it.

SQL ALTER TABLE Statement:

The ALTER TABLE statement is used to add, delete, or modify columns in an existing table.

Syntax:

ALTER TABLE table_name
MODIFY column_name
varchar(new_length);

Example:



Let’s create a table with table_name; “student”

-- create a table
CREATE TABLE students (Sr_No integer,Name varchar(20), Gender integer);

DESCRIBE is used to describe something. Since in database we have tables, that’s why we use DESCRIBE or DESC(both are same) command to describe the structure of a table.

Syntax:

DESCRIBE student;
 OR
DESC student;

Using this command for an above table (in Xampp);

Output:

Now change the size of the column using Alter command

ALTER TABLE student
MODIFY Name
varchar(50);



To see the table structure, use Describe command:

DESCRIBE student;

Output:

Column size is altered from 20 to 50.

For decreasing size of Column “Gender”

ALTER TABLE student
MODIFY Gender
varchar(9);

To see the table structure, use Describe command:

DESCRIBE student;

Output:

Column size is altered from 11 to 9.

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