Обсуждение: [NOVICE] what does t(x) in select x from generate_series(1, 10) as t(x) stand for?

is 

select x from generate_series(1, 10) as t(x);

different from

select x from generate_series(1, 10) as x;

both statements seem to produce the same result in pgAdmin4 (i'm using postresql version 10)

"David G. Johnston" <david.g.johnston@gmail.com> writes:
> On Wednesday, November 8, 2017, john snow <ofbizfanster@gmail.com> wrote:
>> is
>> select x from generate_series(1, 10) as t(x);
>> different from
>> select x from generate_series(1, 10) as x;

> Not sure about the pgAdmin part but t(x) means that you are aliasing the
> table result of the generate_series call to the name "t" and that
> tables' first (and in this case only) column is aliased to the name "x".

Right.

>   The x in the select is then that first column.  In the "as x" variant all
> you've done is alias the table to the name "x" and the "x" in the select
> refers to the table.  Not able to confirm right now but the first result
> should yield a column of type bigint while the second should a composite
> whose only column is a bigint and whose name is "generate_series".

Not sure offhand what happens for a function-returning-composite, but
I'm pretty sure that if the function returns a scalar type, then
SELECT ... from f(...) as x;

is treated the same as
SELECT ... from f(...) as x(x);

Experimentally, these all produce identical results:

select x from generate_series(1, 10) as x;
select x.x from generate_series(1, 10) as x;
select x.* from generate_series(1, 10) as x;

which seems to confirm that.
        regards, tom lane


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