On 2017-08-18 15:57:39 -0500, Justin Pryzby wrote: > On Fri, Aug 18, 2017 at 10:47:37PM +0200, Peter J. Holzer wrote: > > On 2017-08-18 06:37:15 -0500, Justin Pryzby wrote: > > > On Fri, Aug 18, 2017 at 01:01:45PM +0200, Rob Audenaerde wrote: > > > > Can anyone please explain this behaviour? > > > > > > https://www.postgresql.org/docs/9.6/static/sql-expressions.html#SQL-EXPRESSIONS-FUNCTION-CALLS > > > https://www.postgresql.org/docs/9.6/static/rowtypes.html#ROWTYPES-USAGE > > > > Maybe I overlooked it, but I don't see anything in those pages which > > explains why «count» is parsed as a column name in the first example and > > as a function name in the second. > > > > Nor do I see what «count(base.*)» is supposed to mean. It seems to be > > completely equivalent to just writing «count», but the part in > > parentheses is not ignored: It has to be either the table name or the > > table name followed by «.*». Everything else I tried either led to a > > syntax error or to «count» being recognized as a function. So apparently > > columnname open-parenthesis tablename closed-parenthesis is a specific > > syntactic construct, but I can't find it documented anywhere. > > | Another special syntactical behavior associated with composite values is that > |we can use functional notation for extracting a field of a composite value. The > |simple way to explain this is that the notations field(table) and table.field > |are interchangeable. For example, these queries are equivalent: Thanks. I see it now. hp -- _ | Peter J. Holzer | we build much bigger, better disasters now |_|_) | | because we have much more sophisticated | | | hjp@xxxxxx | management tools. __/ | http://www.hjp.at/ | -- Ross Anderson <https://www.edge.org/>
Attachment:
signature.asc
Description: Digital signature
