Pull 5 random records from mysql database [closed]

问题:

I am trying to write a php / mysql script that will pull 5 random records from the DB and display them. At the moment I am using the following to pull one record out and display it in a module, but im not sure how to pull out 5 at a time only. I will have approx 200-300 records in the DB in total.

I am currently using the following code to pull the single record out at random :

<?php
$result = mysql_query("SELECT * FROM `zgjzb_chronoforms_data_submitbusiness` ORDER BY     RAND() LIMIT 0,4;");
$row = mysql_fetch_array($result);
?>

回答1:

You don't want to use ORDER BY RAND(). MySQL has to build a temporary table. If your table has a unique id column, something like this is much better:

SELECT * FROM `zgjzb_chronoforms_data_submitbusiness` 
WHERE id >= (SELECT FLOOR( MAX(id) * RAND()) FROM `table` )
ORDER BY id LIMIT 1;

See this blog post for other approaches that work well in php.