"" <donniehan@126.com> writes:
> postgres=# select * from a limitkkk; ---->(seems equal "limit null")
> Should pg throws a syntax error?
If we did, we'd be violating the SQL standard. The "limitkkk"
is a perfectly valid table alias. There's no AS in front of it,
but unfortunately the spec allows and even encourages people to
omit AS.
regards, tom lane