I have 1000 questions in the Question Model. How do I select 50 questions out of the 10000 randomly using Yii criteria ??
I am using Mysql as the Db
So far I have tried with the following
$criteria = new CDbCriteria;
$criteria->limit = 50;
$criteria->select = array('id');
$criteria->addCondition('chapter = xyz');
If you are using MySQL then it's:
$criteria->order = 'RAND()';
(updated from @topher answer)
Using this technique on a large number of rows will take a long time ( source ):
As soon as you have 10000 rows the overhead for sorting the rows becomes important.
In this case, refer to these answers:
The easiest solution: mysql's order by rand
$criteria->order('RAND()');
However from http://jan.kneschke.de/projects/mysql/order-by-rand/
As soon as you have 10000 rows the overhead for sorting the rows becomes important.
How to efficiently get random rows has been already been answered: MySQL select 10 random rows from 600K rows fast
$criteria->order(array('RAND()'));
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