Hello,
Today I've mistyped a SELECT (effectively omitting the FROM clause):
$ SELECT COUNT(*) my_table;
my_table
----------
1
(1 row)
Apparently, my_table was treated as an alias to the COUNT(*)
expression. This has been discussed before, e.g. here:
http://archives.postgresql.org/pgsql-general/2011-03/msg00331.php
OK, but why it gives 1, and not 0?
A hint might be that if you try "SELECT 1+1, COUNT(*)" or any other
SELECT query w/o the FROM list, the result set always(?) consists of
exactly 1 row.
But does it really make sense? You cannot run a "SELECT *" w/o the
FROM list, and why "COUNT(*)" on empty FROM list would return a value
greater than on e.g. FROM empty_table?
I understand that there's really not much point in running COUNT w/o
the FROM list, but maybe we should just disallow COUNT(*) with empty
FROM list? It will also save from interpreting the result "1" as the
number of rows in the "table" when you mistakenly forgot to add FROM.
--
Regards,
Alex
