How to write mysql primary key auto-increment

There are only two steps to configure primary key auto-increment in MySQL: 1. Specify the primary key and use the PRIMARY KEY keyword when creating the table; 2. Use the ALTER TABLE command to modify the primary key column and specify the AUTO_INCREMENT attribute to automatically increment the primary key. key value.

How to configure primary key auto-increment in MySQL

Configuring primary key auto-increment in MySQL is very simple. Here's how to do it:

Step 1: Specify the primary key when creating the table

When creating the table, use the PRIMARY KEY keyword to specify the Column set as primary key:

<code class="sql">CREATE TABLE table_name (
  id INT NOT NULL AUTO_INCREMENT,
  name VARCHAR(255) NOT NULL,
  age INT NOT NULL
);</code>

Step 2: Specify the AUTO_INCREMENT attribute

AUTO_INCREMENT attribute instructs MySQL when inserting new Automatically increment the primary key value when rowing:

<code class="sql">ALTER TABLE table_name
MODIFY COLUMN id INT NOT NULL AUTO_INCREMENT;</code>

Notes:

• Make sure the data type of the primary key column matches the type of value you want to automatically increment ( For example, for a numeric primary key, use INT; for a string primary key, use VARCHAR).
• The AUTO_INCREMENT attribute can only be set for a single column.
• When a new row is inserted, the next available value is automatically generated and inserted into the primary key column.
• If there is already data in the table, please ensure that the primary key value is unique before enabling AUTO_INCREMENT.

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