-- The closed_linestring table is created with a single linestring column.

CREATE TABLE closed_linestring (ln1 ST_LineString);

-- The INSERT statements insert two records into the closed_linestring table.
-- The first record is not a closed linestring, while the second is.
INSERT INTO closed_linestring VALUES( 
   ST_LineFromText('linestring (10.02 20.01,10.32 23.98,11.92 25.64)', 1000) 
);

INSERT INTO closed_linestring VALUES( 
   ST_LineFromText('linestring (10.02 20.01,11.92 35.64,25.02 34.15,19.15 33.94,10.02 20.01)',1000) 
);

-- The query returns the results of the ST_IsClosed function.
-- The first row returns t (FALSE) because the linestring is not closed,
-- while the second row returns t (TRUE) because the linestring is closed.

SELECT ST_IsClosed(ln1) Is_it_closed 
   FROM closed_linestring;

-- The closed_mlinestring table is created with a single
-- ST_MultiLineString column.

CREATE TABLE closed_mlinestring (mln1 ST_MultiLineString);

-- The INSERT statements insert a ST_MultiLineString record that is
-- not closed and another that is.
INSERT INTO closed_mlinestring VALUES( 
   ST_MLineFromText('multilinestring ((10.02 20.01,10.32 23.98,11.92 25.64),(9.55 23.75,15.36 30.11))',1000) 
);

INSERT INTO closed_mlinestring VALUES( 
   ST_MLineFromText('multilinestring ((10.02 20.01,11.92 35.64,25.02 34.15,19.15 33.94,10.02 20.01),(51.71 21.73,73.36 27.04,71.52 32.87,52.43 31.90,51.71 21.73))',1000) 
);

-- The query lists the results of the ST_IsClosed function.
-- The first row returns f (FALSE) because the multilinestring is not closed.
-- The second row returns t (TRUE) because the multilinestring stored in the
-- mln1 column is closed. A multilinestring is closed if all of its
-- linestring elements are closed.

SELECT ST_IsClosed(mln1) Is_it_closed 
   FROM closed_mlinestring;