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MySQL AUTO_INCREMENT
MySQL AUTO_INCREMENT
In MySQL, the AUTO_INCREMENT attribute is used to automatically generate unique values for a column, typically for a primary key. It automatically increments the value by 1 for each new row inserted into the table.
Key Features of AUTO_INCREMENT:
- Usually applied to a column with the
PRIMARY KEYorUNIQUEconstraint. - Automatically starts from 1 by default.
- Can be manually set to start from a specific value.
- Supports only integer types (
INT,BIGINT,TINYINT, etc.).
Syntax for AUTO_INCREMENT
CREATE TABLE table_name ( column_name INT AUTO_INCREMENT, other_column data_type, PRIMARY KEY (column_name) );
Create a Table with AUTO_INCREMENT
The following SQL statement defines the "student_id" column to be an auto-increment primary key field in the "Persons" table:
Example
CREATE TABLE students (
student_id INT AUTO_INCREMENT,
student_name VARCHAR(50) NOT NULL,
age INT,
PRIMARY KEY (student_id)
);
To let the AUTO_INCREMENT sequence start with another value, use the following SQL statement:
Example
ALTER TABLE students AUTO_INCREMENT = 100;