One method is to pass an argument to RAND() - that is called the seed.
See How can i optimize MySQL's ORDER BY RAND() function?įor ways to optimize it How do I select random rows from a table with limit and no duplicates? Note that order by rand() can be especially slow on large tables. So you'd end up with $query = $conn->prepare('SELECT img_id, title, file_loc FROM images order by rand() limit 2') You could use SELECT img_id, title, file_loc FROM images order by rand() limit 2 If you order by random, you're going to have a terrible table-scan on your hands, and the word quick doesn't apply to such a solution.ĭon't do that, nor should you order by a GUID, it has the same problem. The reason for the skewing is that id's following such holes will have a higher chance of being picked than ones that follow another id. If there are holes here and there but mostly sequential values, and you don't care about a slightly skewed randomness, grab the max value, calculate an id, and select the first row with an id equal to or above the one you calculated. If you know the id's are sequential without holes, you can just grab the max and calculate a random id. Grab all the id's, pick a random one from it, and retrieve the full row. See the article for more advanced examples quick selection of a random row from a large table in mysql This supposes that the distribution of ids is equal, and that there can be gaps in the id list. MySQL select 10 random rows from 600K rows fastĪ great post handling several cases, from simple, to gaps, to non-uniform with gaps.įor most general case, here is how you do it: SELECT name
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