[postgis-users] Extent on multiple tables

[strk at refractions.net]

You might try:

	select extent(g) from (
		select the_geom from table1
		union all
		select the_geom from table2
	) as foo;

Consider also using the estimated_extent() function, which should
give you a much faster result.

--strk;

On Fri, Oct 21, 2005 at 12:00:17PM +0200, Lars Rößiger wrote:
> Hello,
> 
> is there a possibility to use the Extent-function on multiple tables in
> one query? My map layers (built-up areas, waterlines, etc.) are in
> separate tables, but to build the map I need to know the cumulative
> Extent of all layers. I tried INNER JOIN and even subselects within the
> Extent-function -- without success.
> 
> Thank you,
> Lars
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