What are the time functions of Mysql

Editor to share with you what the time functions of Mysql, I believe that most people do not know much, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to know it!

Mysql has plenty of time functions.

Filter conditions with seconds not equal to 0 in 1.mysql query time

Sql code

SECOND (t.file_time)

two。 Current time

Sql code

Now ()

3. A day ago,

Sql code

Select DATE_SUB (curdate (), INTERVAL 1 DAY)

4.timestamp default value

The weird problem of mysql timestamp field

Create a table statement:

Sql code

CREATE TABLE `testtimestamp` (

`id` INT NOT NULL AUTO_INCREMENT

`file_ time`TIMESTAMP NOT NULL

`scan_ time`TIMESTAMP NULL

`created` TIMESTAMP NOT NULL

`modified` TIMESTAMP NOT NULL

PRIMARY KEY (`id`)

) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8

After execution, the default value of file_time is CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP

The default value of scan_time is NULL

The default values for created and modified are '0000-00-0000: 00: 00'

It's a strange question that the first timestamp field of the creation statement is CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP

And when file_time is in update, if it is not in the set group, it will default to now ()!

This results in a default value, and if this field is not present in the update statement, the current time is populated by default.

Type of modification:

Sql code

ALTER TABLE `database`.`tablename` CHANGE COLUMN `columname`columname` TIMESTAMP NOT NULL DEFAULT '0000-00-0000: 0000'

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