Patrick Krecker wrote > I encountered this today and it was quite surprising: > > select version(); > version > > ------------------------------------------------------------------------------------------------------ > PostgreSQL 9.3.5 on x86_64-unknown-linux-gnu, compiled by gcc (Ubuntu > 4.8.2-19ubuntu1) 4.8.2, 64-bit > > create table foo as (select generate_series(1,3)); > > As expected, the following fails: > > select count from foo; > ERROR: column "count" does not exist > LINE 1: select count from foo; > ^ > But if I change the syntax to something I thought was equivalent: > > select foo."count" from foo; > count > ------- > 3 > (1 row) > > It works! This was quite surprising to me. Is this expected behavior, that > you can call an aggregate function without any parentheses (I can't find > any other syntax that works for count() sans parentheses, and this > behavior > doesn't occur for any other aggregate)? That fact that this is an aggregate function is beside the point - the syntax works for any function. The following two expressions are equivalent: count(foo) = foo.count I do not immediately recall where this is documented but it is. It should probably be documented or cross-referenced at: http://www.postgresql.org/docs/9.3/static/sql-syntax-calling-funcs.html#SQL-SYNTAX-CALLING-FUNCS-NAMED but alas that is not so. The basic idea is to hide the function invocation and allow for syntactically similar derived columns to be described. (goes looking) 4.2.6 - the note therein: http://www.postgresql.org/docs/9.3/static/sql-expressions.html#FIELD-SELECTION pointing to 35.4.3 http://www.postgresql.org/docs/9.3/static/xfunc-sql.html#XFUNC-SQL-COMPOSITE-FUNCTIONS This relies on the rule that every table automatically has an implicit type created and so a "composite function" can act on that type. The "foo." reference in your example is technically referring to the type "foo" and not the table "foo". David J. -- View this message in context: http://postgresql.nabble.com/Strange-error-message-when-reference-non-existent-column-foo-count-tp5831200p5831204.html Sent from the PostgreSQL - general mailing list archive at Nabble.com. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
