Changing Table Structure in SQL with Alter Table
If you have worked with SQL, chances are you have encountered situations where you need to change the structure of an existing table. The ALTER TABLE command is a powerful tool in SQL that allows us to make various modifications, such as adding or removing columns, changing the data type of a column, and even renaming a table or column.
Assume you want to add a new column to a table. Or perhaps you need to change the name of an existing column. These are just some of the scenarios where ALTER TABLE can be very useful. Proper use of ALTER TABLE can help you refine your data structure without losing data.
In large projects, especially, modifying the structure of data repositories may happen often. Data patterns may evolve over time, and the ability to swiftly and effectively amend tables without significant side effects is a major advantage. For developers, using ALTER TABLE simplifies complex tasks, enabling them to perform intricate operations with straightforward commands.
Let’s clarify this topic with a simple example. Imagine we have a table named "students" that holds information about students. Now suppose we need to add a new column named "phone_number" to track students' phone numbers. Using ALTER TABLE, this task can be accomplished very easily.
ALTER TABLE students ADD phone_number VARCHAR(15);
Code Explanation:
ALTER TABLE students ADD phone_number VARCHAR(15);This command adds a new column named
phone_number to the students table. The data type of this column is VARCHAR(15), which means this column can hold a string with a maximum length of 15 characters suitable for a phone number.