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    <p>Wow. That's a complicated way to do something very simple. Try this:</p> <p>Assuming you have sequential ids (otherwise you could get no rows).</p> <pre><code>create view random_prova as select * from prova where id = (select min(id) from prova) + floor(RAND(0) * (select max(id) - min(id) from prova)); </code></pre> <p>This will give you 1 random row.</p> <p>To get multiple rows, either loop in a stored procedure or server program until you get enough rows, or programatically create a query that employs union. eg, this will give you 3 random rows:</p> <pre><code>select * from random_prova union select * from random_prova union select * from random_prova; </code></pre> <p>Note that using RAND(0) instead of RAND() means getting a different random number for each invocation. RAND() will give the same value for each invocation in the one statement (so using RAND() with union won't give you multiple rows).</p> <p>There are some shortcomings with using union - it is possible to get the same row twice by chance. Programatically calling this until you get enough rows is safer.</p> <p>To give better performance, use something like java to randomly select the ids for a simple query like </p> <pre><code>select * from prova where id in (...) </code></pre> <p>and have java (or perl or whatever) fill in the list with random ids - you would avoid the inefficiency of having to get the id range every time.</p> <p>Post if your ids are not sequential - there is an efficient way, but I its explanation is long. </p>
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    1. POSelect N random records per group
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    1. USBohemian
    1. USBohemian
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    1. COYou could simply exclude the selected row from the list in random_prova. 1 way of doing this is to push the selected values into an array. Exclude those within that array. But other methods are available too.
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      1. USSyed Abdul Rahman
    2. COthanks for your reply. Maybe I'm wrong but it seems to me that you didn't consider that I need N different records from each group. It can occur that ids are not consecutive. I'm looking for a sql solution without involving any programming language. @Syed. I don't know how to implement efficiently your advice.
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      1. USNicola Cossu
 

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