Re: UNION not working... why?

Stefan Schwarzer <stefan(dot)schwarzer(at)grid(dot)unep(dot)ch> writes:
> But now, I have another problem in this context. If I use text in the
> SELECT statement (so, that the final output gives me the name of the
> selected variables, plus the year and the value) than I get this
> error message: ERROR: failed to find conversion function from
> "unknown" to text

[squint...] Try casting those literals to text explicitly, ie
SELECT 'pop_density'::text AS name. There's some code in there
that makes this work for simple UNION cases, but maybe not so much
for select with a left join and order by and limit inside a union :-(

regards, tom lane