ST_IsRing
Signature
BOOLEAN ST_IsRing(GEOMETRY geom);Description
Return TRUE if geom is a closed and simple LINESTRING or
MULTILINESTRING; NULL otherwise.
Implements the OpenGIS Simple Features Implementation Specification for SQL version 1.2.1.
Examples
SELECT ST_IsRing('LINESTRING(2 1, 1 3, 6 6, 2 1)');
-- Answer: TRUE
SELECT ST_IsRing('LINESTRING(2 1, 1 3, 6 6)');
-- Answer: FALSE
SELECT ST_IsRing('LINESTRING(2 1, 1 3, 6 6, 5 7, 5 2, 2 1)');
-- Answer: FALSE
SELECT ST_IsRing('LINESTRING(2 1, 1 3, 6 6, 5 7, 5 2)');
-- Answer: FALSE
SELECT ST_IsRing('MULTILINESTRING((0 2, 3 2, 3 6, 0 6, 0 2),
(5 0, 7 0, 7 1, 5 1, 5 0))');
-- Answer: TRUE
SELECT ST_IsRing('MULTILINESTRING((0 2, 3 2, 3 6, 0 6, 0 1),
(5 0, 7 0, 7 1, 5 1, 5 0))');
-- Answer: FALSE