How to add, modify and delete MySQL data table field operation guide
Apr 11, 2025 pm 05:42 PMField operation guide in MySQL: Add, modify, and delete fields. Add field: ALTER TABLE table_name ADD column_name data_type [NOT NULL] [DEFAULT default_value] [PRIMARY KEY] [AUTO_INCREMENT] Modify field: ALTER TABLE table_name MODIFY column_name data_type [NOT NULL] [DEFAULT default_value] [PRIMARY KEY]
MySQL Data Table Field Operation Guide: Add, Modify and Delete
In a MySQL database, fields are the basic units for storing data in a table. Adding, modifying, and deleting fields are common data table management tasks. This article will explain in detail how to perform these operations.
Add fields
grammar:
<code class="sql">ALTER TABLE table_name ADD column_name data_type [NOT NULL] [DEFAULT default_value] [PRIMARY KEY] [AUTO_INCREMENT]</code>
Example:
<code class="sql">ALTER TABLE users ADD email VARCHAR(255) NOT NULL</code>
This adds a VARCHAR(255) field named email to the users table and sets it to non-empty.
Modify fields
grammar:
<code class="sql">ALTER TABLE table_name MODIFY column_name data_type [NOT NULL] [DEFAULT default_value] [PRIMARY KEY] [AUTO_INCREMENT]</code>
Example:
<code class="sql">ALTER TABLE users MODIFY name VARCHAR(100)</code>
This will change the data type of the name field in the users table to VARCHAR(100).
Delete fields
grammar:
<code class="sql">ALTER TABLE table_name DROP COLUMN column_name</code>
Example:
<code class="sql">ALTER TABLE users DROP COLUMN email</code>
This will delete the email field from the users table.
Notes:
- Before performing field operations, make sure you have sufficient permissions.
- Field modifications may affect existing data. Please make careful modifications.
- Deleting a field will delete all data in that field forever.
- When adding or modifying the primary key field, you need to re-index.
- The auto-increment field can only be set when adding fields.
The above is the detailed content of How to add, modify and delete MySQL data table field operation guide. For more information, please follow other related articles on the PHP Chinese website!

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