In Sql queries can I use the result of a select clause using aggregate functions as an expression for a comparison?
For example:
x
HAVING COUNT(a) = SELECT COUNT(b) FROM c WHERE b=1
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Answer
Yes, you can do this. You just need parentheses as you would with any subquery:
HAVING COUNT(a) = (SELECT COUNT(b) FROM c WHERE b=1)
Note that count(b)
is not necessary when you know that b
is not NULL
. There is no need to check for NULL
values, so:
HAVING COUNT(a) = (SELECT COUNT(*) FROM c WHERE b = 1)