How can to select a random row from a MySQL database in PHP?

database, mysql, php

Solution

You have a relatively small amount of data, so the simplest method is:

select q.*
from questions q
order by rand()
limit 6;

In this query, the `order by` takes the longest amount of time. Ordering 2,000 rows might be noticeable. A simple fix is to reduce the number of rows being ordered. One method is:

select q.*
from questions q cross join
     (select count(*) as cnt from questions) m
where rand() < 100 / m.cnt
order by rand()
limit 6;

The `where` selects about 100 rows randomly and then orders those to select 6. You are pretty much guaranteed that the `where` will always choose at least 6 rows.

Problem

I have a database table `questions` on a online web server with 2000+ rows and I need to get 6 randomly selected rows. They must be different so that one question is not two times in the list array of 6 questions. How can I achieve this?

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