What Command Is Used to Change the Data Type of a Column?


Scott Campbell

What Command Is Used to Change the Data Type of a Column?

Changing the data type of a column is a common task when working with databases. Whether you need to convert a string to an integer or change the length of a character column, knowing the right command to use can save you time and effort. In this tutorial, we will explore the command used to modify the data type of a column in SQL.

To change the data type of a column, we use the ALTER TABLE statement combined with the MODIFY COLUMN clause. This powerful command allows us to alter various aspects of a column, including its data type.

Here’s an example of how we can use this command:


ALTER TABLE table_name
MODIFY COLUMN column_name new_data_type;

The table_name parameter represents the name of the table containing the column we want to modify. The column_name parameter specifies which column should be altered. Lastly, new_data_type denotes the desired data type for that particular column.

Let’s consider an example scenario where we have a table called “employees” with a “salary” column that is currently defined as an integer. However, due to changing requirements, we now need this column to store decimal values as well.


ALTER TABLE employees
MODIFY COLUMN salary decimal(10, 2);

In this example, we are using the ALTER TABLE statement on the “employees” table and modifying its “salary” column. By specifying “decimal(10, 2)” as the new data type, we ensure that our salary values will be stored with two decimal places.

It is important to note that altering a column’s data type can have implications for existing data. For instance, if you change a column’s data type from integer to decimal, any non-integer values in that column may be truncated or rounded.

  • Make sure to back up your data before performing any modifications to prevent potential loss.
  • Consider the impact of the data type change on any dependent objects or queries.

To summarize, when you need to change the data type of a column in a SQL table, use the ALTER TABLE statement with the MODIFY COLUMN clause. Specify the table name, column name, and new data type to accomplish this task. Remember to handle potential consequences and take precautions to ensure a smooth transition.

In conclusion,

Changing the data type of a column is an essential operation in database management. With the ALTER TABLE statement and the MODIFY COLUMN clause, you can easily modify a column’s data type according to your requirements. Just remember to consider the impact on existing data and take necessary precautions before making any changes.

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    Now that you know how to change the data type of a column using SQL commands, feel free to experiment with different scenarios in your own database projects!