MySQL methods and functions for querying time and date

MySQLIn applications, date and queries are very common. For example, you want to check the data of a certain day, a certain week, or a certain month, query the number of days between two dates, query what day of the week a certain day is, etc. The following will introduce the related MySQL time and date functions, and their specific usage.

NOW() function

MYSQL Is there a getdate() function like MSSQL? Yes, it's NOW().

mysql> SELECT now();
+---------------------+
| now()               |
+---------------------+
| 2011-10-27 09:49:42 |
+---------------------+
1 row in set

NOW() function returns the current date and time.

DATEDIFF() Function

DATEDIFF() function returns the number of days between two dates.

DATEDIFF(expr,expr2)

DATEDIFF() Returns the number of days between the start time expr and the end time expr2. Expr and expr2 are dates or date-and-time expression. Only the date portion of these values ​​is used in the calculation.

mysql> SELECT DATEDIFF('2011-10-27','2011-09-05') AS DiffDate;
+----------+
| DiffDate |
+----------+
|       52 |
+----------+
1 row in set

Query the data within a week

mysql> SELECT title FROM table WHERE datediff(FROM_UNIXTIME(date),now()) > -7;
+------------------------------------+
| title                         |
+------------------------------------+
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+------------------------------------+
24 rows in set

The same query can be used for a month, a year, or any number of days.

To query the day, you can write like this:

mysql> SELECT title FROM table WHERE datediff(FROM_UNIXTIME(date),now()) >= 0;
+----------------------------+
| post_title                 |
+----------------------------+
| 网站运营需要了解的一些规律 |
| 勤于思考才能善于架构       |
+----------------------------+
2 rows in set

To query the day of the week that a certain day is

DAYNAME(date)

Return the name of the working day corresponding to date.

mysql> SELECT DAYNAME( NOW() );
+------------------+
| DAYNAME( NOW() ) |
+------------------+
| Thursday         |
+------------------+
1 row in set

To query what day of the week the date is, write this:

mysql> SELECT DAYOFWEEK( NOW() );
+--------------------+
| DAYOFWEEK( NOW() ) |
+--------------------+
|                  5 |
+--------------------+
1 row in set

Return the corresponding date (1 = Sunday, 2 = Monday, ..., 7 = Saturday) WeekdayIndex. These index values ​​comply with ODBC standards.

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