mysql auto_increment code example

Example 1: mysql set id auto increment

ALTER TABLE users AUTO_INCREMENT=1001;

Example 2: add auto_increment column to existing table mysql

ALTER TABLE `users` ADD `id` INT NOT NULL AUTO_INCREMENT PRIMARY KEY

ALTER TABLE `users` ADD `id` INT NOT NULL AUTO_INCREMENT UNIQUE FIRST

Example 3: insert into auto increment mysql

/* To insert into an auto incrementing field without specifing every column in
the table, you can use the key word default in the place of the auto 
incrementing column*/

INSERT INTO my_table VALUES(default, "test1", 222)
/*VS */
INSERT INTO my_table(name, num) VALUES("test1", 222)
/*Having to type out all of the column names except the auto incrementing one
can be very tedious when you have many columns, just use the keyword defualt
instead and you only have to type it once.

Example 4: create a table with an id in mysql

CREATE TABLE DemoT (
    Personid int NOT NULL AUTO_INCREMENT,
    LastName varchar(111) NOT NULL,
    FirstName varchar(111),
    Age int,
    PRIMARY KEY (Personid)
);

Example 5: auto_increment mysql

ALTER TABLE User AUTO_INCREMENT = 1;

Example 6: auto increment column in mysql query results

SET @auto_increment=0;
SELECT @auto_increment := @auto_increment+1 AS `No`;

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