Decomposing Dates or Times Using Component-Extraction Functions

5.6.1 Problem

You want to obtain just a part of a date or a time.

5.6.2 Solution

Invoke a function specifically intended for extracting part of a temporal value, such as MONTH( ) or MINUTE( ). For obtaining single components of temporal values, these functions are faster than using DATE_FORMAT( ) for the equivalent operation.

5.6.3 Discussion

MySQL includes many functions for extracting date or time parts from temporal values. Some of these are shown in the following list; consult the MySQL Reference Manual for a complete list. The date-related functions work with DATE, DATETIME, or TIMESTAMP values. The time-related functions work with TIME, DATETIME, or TIMESTAMP values.

Function

Return Value

YEAR( )

Year of date

MONTH( )

Month number (1..12)

MONTHNAME( )

Month name (January..December)

DAYOFMONTH( )

Day of month (1..31)

DAYNAME( )

Day of week (Sunday..Saturday)

DAYOFWEEK( )

Day of week (1..7 for Sunday..Saturday)

WEEKDAY( )

Day of week (0..6 for Monday..Sunday)

DAYOFYEAR( )

Day of year (1..366)

HOUR( )

Hour of time (0..23)

MINUTE( )

Minute of time (0..59)

SECOND( )

Second of time (0..59)

Here's an example:

mysql> SELECT dt,
 -> YEAR(dt), DAYOFMONTH(dt),
 -> HOUR(dt), SECOND(dt)
 -> FROM datetime_val;
+---------------------+----------+----------------+----------+------------+
| dt | YEAR(dt) | DAYOFMONTH(dt) | HOUR(dt) | SECOND(dt) |
+---------------------+----------+----------------+----------+------------+
| 1970-01-01 00:00:00 | 1970 | 1 | 0 | 0 |
| 1987-03-05 12:30:15 | 1987 | 5 | 12 | 15 |
| 1999-12-31 09:00:00 | 1999 | 31 | 9 | 0 |
| 2000-06-04 15:45:30 | 2000 | 4 | 15 | 30 |
+---------------------+----------+----------------+----------+------------+

Functions such as YEAR( ) or DAYOFMONTH( ) extract values that have an obvious correspondence to a substring of date values. Some date extraction functions provide access to values that have no such correspondence. One is the day-of-year value:

mysql> SELECT d, DAYOFYEAR(d) FROM date_val;
+------------+--------------+
| d | DAYOFYEAR(d) |
+------------+--------------+
| 1864-02-28 | 59 |
| 1900-01-15 | 15 |
| 1987-03-05 | 64 |
| 1999-12-31 | 365 |
| 2000-06-04 | 156 |
+------------+--------------+

Another is the day of the week, which can be obtained either by name or by number:

  • DAYNAME( ) returns the complete day name. There is no function for returning the three-character name abbreviation, but you can get it easily by passing the full name to LEFT( ):

    mysql> SELECT d, DAYNAME(d), LEFT(DAYNAME(d),3) FROM date_val;
    +------------+------------+--------------------+
    | d | DAYNAME(d) | LEFT(DAYNAME(d),3) |
    +------------+------------+--------------------+
    | 1864-02-28 | Sunday | Sun |
    | 1900-01-15 | Monday | Mon |
    | 1987-03-05 | Thursday | Thu |
    | 1999-12-31 | Friday | Fri |
    | 2000-06-04 | Sunday | Sun |
    +------------+------------+--------------------+
  • To get the day of the week as a number, use DAYOFWEEK( ) or WEEKDAY( )but pay attention to the range of values each function returns. DAYOFWEEK( ) returns values from 1 to 7, corresponding to Sunday through Saturday. WEEKDAY( ) returns values from 0 to 6, corresponding to Monday through Sunday.

    mysql> SELECT d, DAYNAME(d), DAYOFWEEK(d), WEEKDAY(d) FROM date_val;
    +------------+------------+--------------+------------+
    | d | DAYNAME(d) | DAYOFWEEK(d) | WEEKDAY(d) |
    +------------+------------+--------------+------------+
    | 1864-02-28 | Sunday | 1 | 6 |
    | 1900-01-15 | Monday | 2 | 0 |
    | 1987-03-05 | Thursday | 5 | 3 |
    | 1999-12-31 | Friday | 6 | 4 |
    | 2000-06-04 | Sunday | 1 | 6 |
    +------------+------------+--------------+------------+

Another way to obtain individual parts of temporal values is to use the EXTRACT( ) function:

mysql> SELECT dt,
 -> EXTRACT(DAY FROM dt),
 -> EXTRACT(HOUR FROM dt)
 -> FROM datetime_val;
+---------------------+----------------------+-----------------------+
| dt | EXTRACT(DAY FROM dt) | EXTRACT(HOUR FROM dt) |
+---------------------+----------------------+-----------------------+
| 1970-01-01 00:00:00 | 1 | 0 |
| 1987-03-05 12:30:15 | 5 | 12 |
| 1999-12-31 09:00:00 | 31 | 9 |
| 2000-06-04 15:45:30 | 4 | 15 |
+---------------------+----------------------+-----------------------+

The keyword indicating what to extract should be a unit specifier such as YEAR, MONTH, DAY, HOUR, MINUTE, or SECOND. The EXTRACT( ) function is available as of MySQL 3.23.0.

Obtaining the Current Year, Month, Day, Hour, Minute, or Second

The extraction functions shown in this section can be applied to CURDATE( ) or NOW( ) to obtain the current year, month, day, or day of week:

mysql> SELECT CURDATE( ), YEAR(CURDATE( )) AS year,
 -> MONTH(CURDATE( )) AS month, MONTHNAME(CURDATE( )) AS monthname,
 -> DAYOFMONTH(CURDATE( )) AS day, DAYNAME(CURDATE( )) AS dayname;
+------------+------+-------+-----------+------+---------+
| CURDATE( ) | year | month | monthname | day | dayname |
+------------+------+-------+-----------+------+---------+
| 2002-07-15 | 2002 | 7 | July | 15 | Monday |
+------------+------+-------+-----------+------+---------+

Similarly, you can obtain the current hour, minute, and second by passing CURTIME( ) or NOW( ) to a time-component function:

mysql> SELECT NOW( ), HOUR(NOW( )) AS hour,
 -> MINUTE(NOW( )) AS minute, SECOND(NOW( )) AS second;
+---------------------+------+--------+--------+
| NOW( ) | hour | minute | second |
+---------------------+------+--------+--------+
| 2002-07-15 11:21:12 | 11 | 21 | 12 |
+---------------------+------+--------+--------+

5.6.4 See Also

The functions discussed in this recipe provide single components of temporal values. If you want to produce a value consisting of multiple components from a given value, it may be more convenient to use DATE_FORMAT( ). See Recipe 5.5.

Using the mysql Client Program

Writing MySQL-Based Programs

Record Selection Techniques

Working with Strings

Working with Dates and Times

Sorting Query Results

Generating Summaries

Modifying Tables with ALTER TABLE

Obtaining and Using Metadata

Importing and Exporting Data

Generating and Using Sequences

Using Multiple Tables

Statistical Techniques

Handling Duplicates

Performing Transactions

Introduction to MySQL on the Web

Incorporating Query Resultsinto Web Pages

Processing Web Input with MySQL

Using MySQL-Based Web Session Management

Appendix A. Obtaining MySQL Software

Appendix B. JSP and Tomcat Primer

Appendix C. References



MySQL Cookbook
MySQL Cookbook
ISBN: 059652708X
EAN: 2147483647
Year: 2005
Pages: 412
Authors: Paul DuBois

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