mysql table with varchar primary key field - mysql

Question

I have create users table with following structure
CREATE TABLE `users` (
`id` varchar(36) NOT NULL,
`first_name` varchar(100) NOT NULL,
`last_name` varchar(100) NULL,
`email` varchar(100) NOT NULL,
`password` varchar(100) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
I just want to auto filled id value when we insert new row.

Answer 1

If you do wish to generate a uuid in conjuntion with a trigger then your table design has some problems for example
drop table if exists t;
CREATE TABLE t (
`id` varchar(36) not null,
`first_name` varchar(100) NOT NULL,
`last_name` varchar(100) NULL,
`email` varchar(100) NULL,
`password` varchar(100) NULL ,
PRIMARY KEY (`id`)
) ;
drop trigger if exists t;
delimiter $$
create trigger t before insert on t
for each row
begin
set new.id = (select uuid());
end $$
delimiter ;
truncate table t;
insert into t (first_name) values (1),(2);
ERROR 1364 (HY000): Field 'id' doesn't have a default value
And you cannot use a default value because a duplicate error will occur when attempting to insert (2);
And you cannot change the not null to null because the primary key has to have a value.
You can change the id to null and change the primary key to a unique key
drop table if exists t;
CREATE TABLE t (
`id` varchar(36) null,
`first_name` varchar(100) NOT NULL,
`last_name` varchar(100) NULL,
`email` varchar(100) NULL,
`password` varchar(100) NULL ,
unique key (`id`)
) ;
drop trigger if exists t;
create trigger t before insert on t
for each row
set new.id = (select uuid());
truncate table t;
insert into t (first_name) values (1),(2);
select * from t;
+--------------------------------------+------------+-----------+-------+----------+
| id | first_name | last_name | email | password |
+--------------------------------------+------------+-----------+-------+----------+
| 874bd297-adeb-11e8-b404-b8aeed249e19 | 1 | NULL | NULL | NULL |
| 874bda27-adeb-11e8-b404-b8aeed249e19 | 2 | NULL | NULL | NULL |
+--------------------------------------+------------+-----------+-------+----------+
2 rows in set (0.00 sec)

Answer 2

Try id int(11) NOT NULL AUTO_INCREMENT,
CREATE TABLE `users` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`first_name` varchar(100) NOT NULL,
`last_name` varchar(100) NULL,
`email` varchar(100) NOT NULL,
`password` varchar(100) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;

Answer 3

You're trying to make a VARCHAR column auto incrementing. You Can't Do That™.
VARCHAR columns containing the text of integers are notoriously hard to ORDER correctly.
In MySQL, an automatically filled (autoincrementing) ID column must have an integer datatype.
Try changing
`id` varchar(36) NOT NULL,
to
`id` UNSIGNED BIGINT NOT NULL AUTO_INCREMENT,
(I chose UNSIGNED BIGINT because it's the largest integer available, and your choice of 36 in your VARCHAR(36) makes it look like you are expecting an enormous number of rows in this table. But UNSIGNED INT will give you four gigarows, which is probably enough.)
If you choose to use a trigger or some other means to generate the autoincrementing values for your VARCHAR ID column, you will have to do a lot of hard work with transactions to avoid the possibility of duplicate values.
If your client software must see this column as a VARCHAR, you can do it in a view or select. SELECT CAST(id AS VARCHAR(36)) id does it.

Answer 4

Assuming you want an automatically generated GUID for the primary key, this only seems possible in MySql using a trigger.
CREATE TRIGGER before_insert_users
BEFORE INSERT ON users
FOR EACH ROW
BEGIN
IF new.id IS NULL THEN
SET new.id = uuid();
END IF;
END
More information can be found here:
https://www.electrictoolbox.com/mysql-guid-uuid-default-column/

Answer 5

According to Cookbook 3.x:
Rather than using an auto-increment key as the primary key, you may
also use char(36). CakePHP will then use a unique 36 character UUID
(Text::uuid) whenever you save a new record using the Table::save()
method.
Means CakePHP automatically saves a unique 36 character UUID (Text::uuid) whenever you save a new record using the Table::save() method.
Just change
id varchar(36) NOT NULL
to
id char(36) NOT NULL
Hope this will help!