[postgis-users] ST_IsClosed

[Christopher Braune]

Hello PostGIS-Users,

I want to select all closed lines in my dataset. I think the function 
ST_IsClosed is usefull for this task.

I tried the following SQL-Sentence:
 >>
SELECT *, (SELECT ST_IsClosed(lines.linestring) AS tof) FROM 
public.lines WHERE tof='TRUE';
<<

I get this error-message:

 >>
ERROR:  column "tof" does not exist
LINE 3: ...s.linestring) AS tof) FROM public.lines WHERE tof='TRUE'...
                                                         ^
********** Fehler **********

ERROR: column "tof" does not exist
SQL Status:42703
Zeichen:131
<<

Can anybody help me? In general I want to know how I use the 
boolean-results (like ST_IsClosed) in nested queries.

Best regards,
Christopher