ST_IsRing takes an ST_LineString and returns 1 (Oracle) or t (PostgreSQL) if it is a ring (for example, the ST_LineString is closed and simple); otherwise, it returns 0 (Oracle) or f (PostgreSQL).
Oracle
sde.st_isring (ln1 sde.st_geometry)
PostgreSQL
st_isring (ln1 st_geometry)
The ring_linestring table is created with a single ST_LineString column, ln1.
Oracle
CREATE TABLE ring_linestring (ln1 sde.st_geometry);
PostgreSQL
CREATE TABLE ring_linestring (ln1 st_geometry);
The INSERT statements insert three linestrings into the ln1 column. The first row contains a linestring that's not closed and isn't a ring. The second row contains a closed and simple linestring that is a ring. The third row contains a linestring that is closed but not simple because it intersects its own interior. It is also not a ring.
Oracle
INSERT INTO ring_linestring VALUES (
sde.st_linefromtext ('linestring (10.02 20.01, 10.32 23.98, 11.92 25.64)', 0)
);
INSERT INTO ring_linestring VALUES (
sde.st_linefromtext ('linestring (10.02 20.01, 11.92 35.64, 25.02 34.15, 19.15 33.94, 10.02 20.01)', 0)
);
INSERT INTO ring_linestring VALUES (
sde.st_linefromtext ('linestring (15.47 30.12, 20.73 22.12, 10.83 14.13,
16.45 17.24, 21.56 13.37, 11.23 22.56, 19.11 26.78, 15.47 30.12)', 0)
);
PostgreSQL
INSERT INTO ring_linestring VALUES (
st_linestring ('linestring (10.02 20.01, 10.32 23.98, 11.92 25.64)', 0)
);
INSERT INTO ring_linestring VALUES (
st_linestring ('linestring (10.02 20.01, 11.92 35.64, 25.02 34.15, 19.15 33.94, 10.02 20.01)', 0)
);
INSERT INTO ring_linestring VALUES (
st_linestring ('linestring (15.47 30.12, 20.73 22.12, 10.83 14.13,
16.45 17.24, 21.56 13.37, 11.23 22.56, 19.11 26.78, 15.47 30.12)', 0)
);
The query returns the results of the function. The first row returns 0 because the linestrings aren't rings while the second and third rows return 1 because they are rings.
Oracle
SELECT sde.st_isring (ln1) Is_it_a_ring
FROM ring_linestring;
Is_it_a_ring
0
1
1
PostgreSQL
SELECT st_isring (ln1) AS Is_it_a_ring
FROM ring_linestring;
Is_it_a_ring
f
t
t