Selecting a random row using MySQL

vinoaj — Wed, 25 Jul 2007 08:54:58 +0000

There are many examples where you would need to retrieve a random record or more from a set of tables. For example your page template may be cycling through QOTDs, testimonials, offers, specials, and so forth.

To retrieve a random row in MySQL, use the ORDER BY RAND() statement to randomly order the rows of a table. Then use LIMIT x to retrieve the first x rows from the randomised representation of the table.

For example:

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SQL:

/* Retrieve 5 random special offers to display in your e-commerce store's sidebar */
SELECT offer_id
FROM special_offers
ORDER BY RAND()
LIMIT 5

Of course, we can make our query as complex as needed, and then randomly order the resultset.

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SQL:

SELECT so.offer_id, i.title
FROM special_offers so
LEFT JOIN items i ON (so.item_id = i.item_id)
LEFT JOIN item_categories ic ON (i.item_id = ic.item_id)
WHERE ic.category_id = 2344
ORDER BY RAND()
LIMIT 5

Using mysqldump to export a database

admin — Sat, 28 Apr 2007 05:07:41 +0000

mysqldump is a useful utility for dumping the contents of an entire database to an SQL file.

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CODE:

mysqldump --user=dbusername --password=dbpassword db_name_here> db_name_here.sql

By default the --opt option is enabled, which is a shorthand option for specifying the below options. According to the documentation, using this option "... should give you a fast dump operation and produce a dump file that can be reloaded into a MySQL server quickly".

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CODE:

--add-drop-table
--add-locks
--create-options
--disable-keys
--extended-insert
--lock-tables
--quick
--set-charset

VV's Corner » mysql

Selecting a random row using MySQL

Using mysqldump to export a database