How to set the primary key in mysql to increase automatically

Steps to set up an auto-incrementing primary key in MySQL: When creating a table, use the AUTO_INCREMENT keyword on the primary key column. When inserting data, there is no need to specify a primary key value, MySQL will automatically generate an incrementing value. The most recently inserted auto-increment value can be retrieved using the LAST_INSERT_ID() function. Auto-incrementing primary keys only work with integer data types and cannot be used with other data types such as strings or dates. The auto-incremented primary key value will not be reused after deleting the record and cannot be modified.

MySQL primary key auto-increment setting method

1. The concept of primary key

The primary key is a special column in a database table that uniquely identifies each record. It is usually unique and non-null, ensuring that every record in the database has a unique identifier.

2. Auto-increment primary key

Auto-increment primary key is a primary key that automatically increments a value whenever a new record is inserted. This simplifies the developer's job since they don't have to assign key values ​​manually.

3. Set the auto-increment primary key

To create an auto-increment primary key in MySQL, you need to use the AUTO_INCREMENT keyword when creating the table:

<code>CREATE TABLE table_name (
  id INT NOT NULL AUTO_INCREMENT,
  name VARCHAR(255) NOT NULL,
  PRIMARY KEY (id)
);</code>

Among them:

• id column is an auto-incrementing primary key.
• INT The data type of the specified column is integer.
• NOT NULL Ensure that the column cannot be empty.
• AUTO_INCREMENT Specifies that the column should be automatically incremented.
• PRIMARY KEY (id) Specifies this column as the primary key.

4. Insert data

When inserting data, you do not need to specify the value of the auto-incrementing primary key. MySQL will automatically generate a unique incrementing value. For example:

<code>INSERT INTO table_name (name) VALUES ('John Doe');</code>

5. View the auto-increment value

You can use the LAST_INSERT_ID() function to retrieve the recently inserted auto-increment value. For example:

<code>SELECT LAST_INSERT_ID();</code>

6. Note that

• auto-incrementing primary keys can only be used for integer data types (such as INT, BIGINT) and cannot be used with other data types such as strings or dates.
• The auto-incremented primary key value will not be reused after deleting the record. If you delete a record, the key value of that record will be permanently skipped.
• Auto-incrementing primary keys cannot be modified. If you need to change the key value, you need to create a new sequence or use other mechanisms.

The above is the detailed content of How to set the primary key in mysql to increase automatically. For more information, please follow other related articles on the PHP Chinese website!