Re: generic crosstab ?

On Tue, Apr 24, 2012 at 1:01 PM, Andreas <maps(dot)on(at)gmx(dot)net> wrote:

> Hi,
>
> is there a generic solution to dump the result of a query as a crosstab,
> when I can't know how many columns I will need?
>
> E.g. I get something like this:
>
> id, x
> 1, a
> 1, b
> 1, c
> 2, l
> 2, m
>
>
>
Yes. You can provide a query which returns the columns to the version of
the crosstab function which looks like this:

crosstab(text source_sql, text category_sql)
It does exactly what you are looking for. The second query returns the set
of values that act as columns in the final result (the pivot for each row
in the result returned by the first query). This allows the function to
correctly insert a null for any column for which there is no row in the
first query results.