Re: unnest in SELECT

Karl Koster <klkoster(at)optonline(dot)net> wrote:

> I have a couple of questions regarding unnest.
>
> 1) If I issue a select statement "select unnest(vector1) as v from
> some_table", I cannot seem to use the column alias v in a WHERE or
> HAVING clause. I can use it in an ORDER BY or GROUP by clause. Is this
> the way it is supposed to work?

Yes. It's the same as:

test=# select 1 as a where a = 2;
ERROR: column "a" does not exist
LINE 1: select 1 as a where a = 2;

in other words: the column a is unknown for the where-condition at this
time.

>
> 2) If I issue a select statement "select unnest(vector1) as v1,
> unnest(vector2) as v2 from some_table" and vector1 has a length of 3 and
> vector2 has a length of 4, the result set will have 12 rows with the
> data of vector1 repeating 4 times and vector2 repeating 3 times.

Yeah, it's a cross-join.

Andreas
--
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