Synthesizing Dates or Times Using Formatting Functions

5.8.1 Problem

You want to produce a new date from a given date by replacing parts of its values.

5.8.2 Solution

Use DATE_FORMAT( ) or TIME_FORMAT( ) to combine parts of the existing value with parts you want to replace.

5.8.3 Discussion

The complement of splitting apart a date or time value is synthesizing one from its constituent parts. Techniques for date and time synthesis include using formatting functions (discussed here) and string concatenation (discussed in Recipe 5.9).

Date synthesis often is performed by beginning with a given date, then keeping parts that you want to use and replacing the rest. For example, to find the first day of the month in which a date falls, use DATE_FORMAT( ) to extract the year and month parts from the date and combine them with a day value of 01:

mysql> SELECT d, DATE_FORMAT(d,'%Y-%m-01') FROM date_val;
+------------+---------------------------+
| d | DATE_FORMAT(d,'%Y-%m-01') |
+------------+---------------------------+
| 1864-02-28 | 1864-02-01 |
| 1900-01-15 | 1900-01-01 |
| 1987-03-05 | 1987-03-01 |
| 1999-12-31 | 1999-12-01 |
| 2000-06-04 | 2000-06-01 |
+------------+---------------------------+

TIME_FORMAT( ) can be used in a similar way:

mysql> SELECT t1, TIME_FORMAT(t1,'%H:%i:00') FROM time_val;
+----------+----------------------------+
| t1 | TIME_FORMAT(t1,'%H:%i:00') |
+----------+----------------------------+
| 15:00:00 | 15:00:00 |
| 05:01:30 | 05:01:00 |
| 12:30:20 | 12:30:00 |
+----------+----------------------------+

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

Similar book on Amazon

Flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net