Finding the Length of a Month

5.23.1 Problem

You want to know how many days there are in a month.

5.23.2 Solution

Determine the date of its last day, then extract the day-of-month component from the result.

5.23.3 Discussion

To determine the number of days for the month in which a given date occurs, calculate the date for the last day of the month as shown in the previous section, then extract the DAYOFMONTH( ) value from the result:

mysql> SELECT d,
 -> DAYOFMONTH(DATE_SUB(
 -> DATE_ADD(DATE_SUB(d,INTERVAL DAYOFMONTH(d)-1 DAY),INTERVAL 1 MONTH),
 -> INTERVAL 1 DAY))
 -> AS 'days in month'
 -> FROM date_val;
+------------+---------------+
| d | days in month |
+------------+---------------+
| 1864-02-28 | 29 |
| 1900-01-15 | 31 |
| 1987-03-05 | 31 |
| 1999-12-31 | 31 |
| 2000-06-04 | 30 |
+------------+---------------+

5.23.4 See Also

Recipe 5.28 later in this chapter discusses another way to calculate month lengths. Chapter 10 discusses leap year calculations in the context of date validation.

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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