Incorrect table definition; there can be only one auto column and it must be defined as a key

An auto column is a column that automatically generates a unique value for each new row that is inserted into a table. It is commonly used as a primary key to ensure that each row in the table has a unique identifier.

However, when defining a table in SQL, there can only be one auto column and it must be defined as a key. This means that the auto column must be declared as either the primary key or a unique key constraint.

For example, the correct way to define a table with an auto column as a primary key would be:

CREATE TABLE my_table ( id INT AUTO_INCREMENT PRIMARY KEY, name VARCHAR(50), age INT );

In this example, the id column is defined as an auto column using the AUTO_INCREMENT keyword, and it is also declared as the primary key using the PRIMARY KEY keyword.

If you try to define multiple auto columns or an auto column without declaring it as a key, you will receive an error message