PostgreSQL equal aggregate

Question

I'd like to check that all (float) values of a set of records are equal. Something like

SELECT ..., equal(my_field) FROM my_table WHERE ... GROUP BY ...

Where equal(my_field) returns true if all values of my_field are equal.

Answer 1

You could use MIN and MAX aggregates

SELECT min(field)=max(field) WHERE ... GROUP BY...

This doesn't take into account NULL values though. If those may be in the column you have to add a check for that.

Also remember that with floats equality is not always simple to check.