Summarizing with MIN( ) and MAX( )

Summarizing with MIN() and MAX()

7.3.1 Problem

You need to determine the smallest or largest of a set of values.

7.3.2 Solution

Use MIN( ) to find the smallest value, MAX( ) to find the largest.

7.3.3 Discussion

Finding smallest or largest values is somewhat akin to sorting, except that instead of producing an entire set of sorted values, you select only a single value at one end or the other of the sorted range. This kind of operation applies to questions about smallest, largest, oldest, newest, most expensive, least expensive, and so forth. One way to find such values is to use the MIN( ) and MAX( ) functions. (Another way to address these questions is to use LIMIT; see the discussions in Recipe 3.17 and Recipe 3.19.)

Because MIN( ) and MAX( ) determine the extreme values in a set, they're useful for characterizing ranges:

  • What date range is represented by the rows in the mail table? What are the smallest and largest messages sent?

    mysql> SELECT
     -> MIN(t) AS earliest, MAX(t) AS latest,
     -> MIN(size) AS smallest, MAX(size) AS largest
     -> FROM mail;
    +---------------------+---------------------+----------+---------+
    | earliest | latest | smallest | largest |
    +---------------------+---------------------+----------+---------+
    | 2001-05-11 10:15:08 | 2001-05-19 22:21:51 | 271 | 2394482 |
    +---------------------+---------------------+----------+---------+
  • What are the shortest and longest trips in the driver_log table?

    mysql> SELECT MIN(miles) AS shortest, MAX(miles) AS longest
     -> FROM driver_log;
    +----------+---------+
    | shortest | longest |
    +----------+---------+
    | 79 | 502 |
    +----------+---------+
  • What are the lowest and highest U.S. state populations?

    mysql> SELECT MIN(pop) AS 'fewest people', MAX(pop) AS 'most people'
     -> FROM states;
    +---------------+-------------+
    | fewest people | most people |
    +---------------+-------------+
    | 453588 | 29760021 |
    +---------------+-------------+
  • What are the first and last state names, lexically speaking?

    mysql> SELECT MIN(name), MAX(name) FROM states;
    +-----------+-----------+
    | MIN(name) | MAX(name) |
    +-----------+-----------+
    | Alabama | Wyoming |
    +-----------+-----------+

MIN( ) and MAX( ) need not be applied directly to column values. They also work with expressions or values that are derived from column values. For example, to find the lengths of the shortest and longest state names, do this:

mysql> SELECT MIN(LENGTH(name)) AS shortest, MAX(LENGTH(name)) AS longest
 -> FROM states;
+----------+---------+
| shortest | longest |
+----------+---------+
| 4 | 14 |
+----------+---------+

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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