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Editorial Team
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Asked: 2026-05-12T18:04:53+00:00

Lets say you have a table with some winning numbers in it. Any of

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Lets say you have a table with some winning numbers in it. Any of these numbers is meant to be only “won” by one person.

How could I prevent 2 simultaneous web requests that submit the same numbers from both checking and seeing that the numbers is still available and then giving the prize to both of them before the number is marked as no longer being available.

The winning solution in this question feels like what I was thinking of doing, as it can also be applied in most database platforms.

Is there any other common pattern that can be applied to this?

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1 Answer

  1. Editorial Team

    These numbers are randomly generated or something?

    I would rely on the transactional semantics in the database itself: Create a table with two columns, number and claimed, and use a single update:

    UPDATE winners SET claimed=1 WHERE claimed=0 AND number=@num;

    Then check the number of affected rows.

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