edrackham » Featured http://edrackham.com PHP, MySQL, and Other Web Snippets! Wed, 25 Jun 2008 13:38:14 +0000 http://wordpress.org/?v=2.3.3 en Get Random Row with MySQL Without ORDER BY RAND() http://edrackham.com/featured/get-random-row-with-mysql-without-order-by-rand/ http://edrackham.com/featured/get-random-row-with-mysql-without-order-by-rand/#comments Wed, 05 Mar 2008 12:12:24 +0000 Ed fastMySQLrandom row http://edrackham.com/mysql/get-random-row-with-mysql-without-rand/ This is an update to a previous post of mine which uses the RAND() method. Using the following code, you can retrieve a random row much, much faster (MySQL 4.1.x/5.0.x), with thanks to Jan Kneschke:

SELECT <COLUMN> FROM <TABLE> AS r1
JOIN (SELECT ROUND(
  RAND( ) * (
    SELECT MAX( id ) FROM <TABLE>)
  ) AS id
) AS r2
WHERE r1.id >= r2.id
ORDER BY r1.id ASC
LIMIT 1;

Replace:

  • <COLUMN> with the name of the column(s) you wish to retrieve
  • <TABLE> with the name of the table you wish to retrieve the data from

I've tested this with a table with over 660,000 records, and got a response in 0.0200 seconds, whereas with ORDER BY RAND() i got a response in 2.1599 seconds.

Total Number of Rows:

Cardinality

Old Method:

Old Method

New Method:

New Method

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