[postgis-users] Question about Crosses(geometry, geometry)

[TECHER David]

Hi Matt

instead of

select lines.* from lines,polygons where not 
crosses(lines.the_geom,polygons.the_geom)

try

select lines.* from lines where not 
crosses(lines.the_geom,polygons.the_geom)

don't use a call to polygons' table

Matt Doughty a écrit :
>
> Hi List,
>
> I’ve a question about the CROSSES (geometry, geometry) function. I’d 
> like to use it to select lines from a table that do not cross, or 
> intersect, some polygons in a separate table.
>
> The following script lets me select the lines that cross the polygons:
>
> SELECT
>
> lines.*
>
> FROM
>
> lines,
>
> polygons
>
> WHERE
>
> CROSSES(lines.the_geom, polygons.the_geom)
>
> Now I’d like to place a ‘NOT’ before the function CROSSES (-> NOT 
> CROSSES(lines.the_geom, polygons.the_geom), rather naively it seems, 
> as doing that returns me a table with the same geometry as the 
> original layer, but with 30 times more rows (an increase of 400 to 
> 12,000 records). In other words, it hasn’t ‘selected’ and lines out of 
> the layer, merely repeated the table geometry 30 times.
>
> Can anybody explain where I’m going wrong?
>
> Many thanks in advance,
>
> Matt
>
> Matt Doughty
>
> 	
>
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>
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>
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