What are the characteristics of mysql identity columns?

1. The identification column does not have to be matched with the primary key, but it is required to be a key.

2. A table has at most one identity column.

3. The type of the identification column can only be numeric.

By SET auto_increment_increment=3, the identity column can set the step size.

4. The starting value can be set by manual insertion.

Example

DROP TABLE IF EXISTS tab_id;
 
CREATE TABLE tab_id(
id INT PRIMARY KEY AUTO_INCREMENT,
NAME VARCHAR(20)
);
 
INSERT INTO tab_id VALUES(NULL,'john');#可重复执行插入
INSERT INTO tab_id(NAME) VALUES('lucy');
SELECT * FROM tab_id;
 
#自增步长
SET auto_increment_increment=3;

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