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Editorial Team
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Asked: 2026-05-13T00:36:30+00:00

I have learned that SO has put questions and answers in the same table.

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I have learned that SO has put questions and answers in the same table. They say that a question will not have a parent id and answers will have parent IDs. Why is it better to do it this way instead of putting questions and answers in separate tables?

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  1. Editorial Team

    Several reasons:

    • Conceptually questions and answers aren’t really that different from a modelling perspective;
    • It makes it easier to search (one table rather than two);
    • If you’ve ever tried to implement such a system across two tables (and this includes forums where you have posts that start threads and replies) you’ll quickly discover the SQL gets really awkward really fast.

    The best way to look at this problem is to run a particular model through some use cases.

    For example: list all posts by a user in some order (votes, date, etc). Across two tables you end up doing some kind of UNION, which is not really undesirable. If they’re stored in the same table it’s much easier. If you just want to limit it to questions or answers then the same table is still easy as it’s just an extra criteria (eg WHERE parentID IS NULL for questions).

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