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Asked: 2026-05-31T17:25:12+00:00

I have a table similar to this +–+—–+—-+ |ID|Entry|Exit| +–+—–+—-+ |18|32154|NULL| +–+—–+—-+ |19|NULL |NULL|

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I have a table similar to this

+--+-----+----+
|ID|Entry|Exit|
+--+-----+----+
|18|32154|NULL|
+--+-----+----+
|19|NULL |NULL|
+--+-----+----+

When I select AVG(Entry) it correctly gives me 32154, when I select AVG(Exit) it blows up saying “Operand data type void type is invalid for avg operator.”

How can I get NULL as the average for a column that only has NULL values?

Thanks,

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1 Answer

  1. Editorial Team

    The problem is that the Exit column doesn’t have a data type that is compatible with the SUM function.

    You can run this query to see that you indeed get NULL from SUM if all values are NULL (and a proper data type)

    select sum(a) from (select convert(int, null) a union select null) a
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