mysql updated_at use milliseconds since EPOCH as default ON UPDATE - mysql

Question

In my app I am using Sequelize. Now I want to use milliseconds since EPOCH for the updated_at column, so that it looks like:
-------------
updated_at
-------------
1571838511364
-------------
The data definition now looks like:
CREATE TABLE `projects` (
`id` char(36) NOT NULL,
`name` varchar(45) NOT NULL,
`description` varchar(450) NOT NULL,
`active` tinyint(1) NOT NULL DEFAULT '1',
`created_at` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP,
`updated_at` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci
I have done this to the created_at as it is easy to set the default value with Sequelize, but for updated_at, how do I set the default value for ON UPDATE?
I know
SELECT UNIX_TIMESTAMP(current_timestamp()) will give me the current millisecond, so I have:
updatedAt: {
type: Sequelize.STRING,
allowNull: false,
defaultValue: Sequelize.literal(
'UNIX_TIMESTAMP(current_timestamp()) ON UPDATE UNIX_TIMESTAMP(current_timestamp())'
),
},
And this will give me error:
Executing:
ALTER TABLE `ab`.`projects`
CHANGE COLUMN `updated_at` `updated_at` VARCHAR(45) NOT NULL DEFAULT UNIX_TIMESTAMP(current_timestamp()) ON UPDATE UNIX_TIMESTAMP(current_timestamp()) ;
ERROR 1064: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'UNIX_TIMESTAMP(current_timestamp()) ON UPDATE UNIX_TIMESTAMP(current_timestamp()' at line 2
I also tried default value to be:
'UNIX_TIMESTAMP ON UPDATE UNIX_TIMESTAMP'
but I got the same sql error anyway.
How do I achieve my goal so that ON UPDATE will use the current millisecond value?

Answer 1

default value in mysql must a be literal , only exception is using CURRENT_TIMESTAMP() .
https://dev.mysql.com/doc/refman/5.6/en/data-type-defaults.html#data-types-defaults-explicit
unix_timestamp(CURRENT_TIMESTAMP()) is different than CURRENT_TIMESTAMP()
If you want milli-seconds or microsecond you must add a precision to datetime and current_timestamp .
You table will become this with a precision of 4 digits .
CREATE TABLE `projects` (
`id` char(36) NOT NULL,
`name` varchar(45) NOT NULL,
`description` varchar(450) NOT NULL,
`active` tinyint(1) NOT NULL DEFAULT '1',
`created_at` datetime(4) NOT NULL DEFAULT CURRENT_TIMESTAMP(4),
`updated_at` datetime(4) NOT NULL DEFAULT CURRENT_TIMESTAMP(4) ON UPDATE CURRENT_TIMESTAMP(4),
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 ;
A example with sqlfiddle ( http://sqlfiddle.com/#!9/3a85ff/1 )