"Daniel Cristian Cruz" <danielcristian@gmail.com> writes:
> Where it says:
> "Notice how the AS clause is used to relabel the output column. (The AS
> clause is optional.)"
> It's wrong, because it causes an error if executed without it.
Hmm? You can leave off the AS clause if you want:
SELECT city, (temp_hi+temp_lo)/2 AS temp_avg, date FROM weather;
SELECT city, (temp_hi+temp_lo)/2, date FROM weather;
regards, tom lane