[postgis-users] Getting argument of AND must not return a set, when trying to calculate the intersection of a end of a multiline and a polygon

[Dave Potts]

Hi,

I am trying to find the results of an intersection between a multi line 
string and a polygon,  I had assumed that saying something
like

select rt.source, 
av.geom,st_astext(st_startpoint((st_dump((rt.the_geom))).geom)) from 
route_table rt ,
avoid_areas av
where av.valid=true and rt.parent_port_id=80360 and
st_within(av.geom,st_startpoint((st_dump((rt.the_geom))).geom)) =true

might work where rt.the_geom is a multiline  and av.geom is a polygon

but I get the error,
ERROR:  argument of AND must not return a set
LINE 4: st_within(av.geom,st_startpoint((st_dump((rt.the_geom))).geo

any idea what I am doing wrong?

Dave