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Editorial Team
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Asked: 2026-06-08T07:24:39+00:00

Consider the following table: tweets ———————– id tweet class ———————– 1 Foo bar baz!

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Consider the following table:

tweets
-----------------------
id  tweet         class
-----------------------
1   Foo bar baz!  2
2   Lorem ipsum   2
3   Foobar lorem  3
4   Activi set    1
5   Baz baz bar?  3
7   Dolor mez foo 3
8   Samet set bar 1

In reality, the table has 600,000 records, but as indicated in the example table, some ids have been deleted (so the highest id > 600,000). class can be either 1, 2 or 3.

I need a random selection 1200 tweets, 400 of each class. Is this possible to do with one query?

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1 Answer

  1. Editorial Team

    If you have a finite number of possible values for class (3), then it is easily done with a set of UNION queries each having their own ORDER BY RAND() and LIMIT 400:

    (SELECT id, tweet, class FROM tweets WHERE class = 1 ORDER BY RAND() LIMIT 400)
UNION
(SELECT id, tweet, class FROM tweets WHERE class = 2 ORDER BY RAND() LIMIT 400)
UNION
(SELECT id, tweet, class FROM tweets WHERE class = 3 ORDER BY RAND() LIMIT 400)

    For the ORDER BY to be applied to each UNION group, the group must be enclosed in ().

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