ST_Touches

Signature

BOOLEAN ST_Touches(GEOMETRY geomA, GEOMETRY geomB);

Description

Returns TRUE if geomA touches geomB.

Touches means that:

geomA and geomB have at least one point in common.
The interiors of geomA and geomB do not intersect.

Remarks

ST_Touches can only be used to determine the relation between pairs listed here: (POLYGON, POLYGON), (POLYGON, LINESTRING), (POLYGON, POINT), (LINESTRING, LINESTRING) and (LINESTRING, POINT). The relation (POINT, POINT) is excluded.
GEOMETRYCOLLECTIONs are not taken into account.

Note

Implements the OpenGIS Simple Features Implementation Specification for SQL version 1.2.1

Warning

This predicate does not yet support spatial indices, but it will in a future release. Use it in conjunction with && operator. See here for more details.

Examples

Cases where `ST_Touches` is true

SELECT ST_Touches(geomA, geomB) FROM input_table;
-- Answer:    TRUE

geomA POLYGON	geomB POLYGON
POLYGON((1 1, 4 1, 4 5, 1 5, 1 1))	POLYGON((4 2, 7 2, 7 6, 4 6, 4 2))

geomA POLYGON	geomB LINESTRING
POLYGON((1 1, 4 1, 4 5, 1 5, 1 1))	LINESTRING(2 5, 7 5)

geomA POLYGON	geomB POINT
POLYGON((1 1, 4 1, 4 5, 1 5, 1 1))	POINT(4 3)

geomA LINESTRING	geomB LINESTRING
LINESTRING(2 1, 5 3, 2 6)	LINESTRING(1 3, 3 5)

geomA LINESTRING	geomB POINT
LINESTRING(2 1, 5 3, 2 6)	POINT(2 6)

geomA POLYGON	geomB MULTIPOLYGON
POLYGON((1 1, 4 1, 4 5, 1 5, 1 1))	MULTIPOLYGON(((4 2, 7 2, 7 6, 4 6, 4 2)), ((0 6, 1 6, 1 7, 0 7, 0 6)))

geomA POLYGON	geomB MULTILINESTRING
POLYGON((1 1, 4 1, 4 5, 1 5, 1 1))	MULTILINESTRING((2 5, 7 5), (6 1, 6 4))

geomA POLYGON	geomB MULTIPOINT
POLYGON((1 1, 4 1, 4 5, 1 5, 1 1))	MULTIPOINT((4 3), (6 2))

geomA POLYGON	geomB POLYGON
POLYGON((1 1, 4 1, 4 5, 1 5, 1 1))	POLYGON((4 5, 7 5, 7 6, 4 6, 4 5))

Cases where `ST_Touches` is false

SELECT ST_Touches(geomA, geomB) FROM input_table;
-- Answer:    FALSE

geomA POLYGON	geomB POLYGON
POLYGON((1 1, 4 1, 4 5, 1 5, 1 1))	POLYGON((3 4, 7 4, 7 6, 3 6, 3 4))