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Asked: 2026-05-11T09:17:29+00:00

I’m designing a database schema, and I’m wondering what criteria I should use for

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I’m designing a database schema, and I’m wondering what criteria I should use for deciding whether each column should be nullable or not.

Should I mark as NOT NULL only those columns that absolutely must be filled out for a row to make any sense at all to my application?

Or should I mark all columns that I intend to never be null?

What are the performance implications of small vs large numbers of NOT NULL columns?

I assume lots of NOT NULL columns would slow down inserts a bit, but it might actually speed up selects, since the query execution plan generator has more information about the columns..

Can someone with more knowledge than me give me the low-down?

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1 Answer

  1. Honestly, I’ve always thought NOT NULL should be the default. NULL is the odd special case, and you should make a case for it whenever you use it. Plus it’s much easier to change a column from NOT NULL to nullable than it is to go the other way.

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