ST_DIFFERENCE()

All functions > GEOSPATIAL > ST_DIFFERENCE()

Returns the geometry/geography representing the point set difference of A minus B.

Signatures

Difference

Returns: A minus B

ST_DIFFERENCE(geo1: T, geo2: T) → GEOMETRY or GEOGRAPHY

With:

• T : Custom types: GEOM_POINT | GEOM_LINESTRING | GEOM_POLYGON | GEOM_MULTIPOINT | GEOM_MULTILINESTRING | GEOM_MULTIPOLYGON | GEOM_MULTIANY | GEOG_POINT | GEOG_LINESTRING | GEOG_POLYGON | GEOG_MULTIPOINT | GEOG_MULTILINESTRING | GEOG_MULTIPOLYGON | GEOG_MULTIANY

Signature notes:

• Returns the part of A that does not intersect B
• If A is fully within B, returns an empty geometry
• Order matters: ST_DIFFERENCE(A, B) is not the same as ST_DIFFERENCE(B, A)
• ST_ASTEXT output may use either winding direction for rings; consumers that require strict OGC exterior orientation should normalize before exchange
• Both inputs must be the same type family
• Returns NULL if either input is NULL

Examples

SELECT
    f1 := ST_ASTEXT(ST_DIFFERENCE(ST_GEOMFROMTEXT('POLYGON ((0 0, 3 0, 3 3, 0 3, 0 0))'), ST_GEOMFROMTEXT('POLYGON ((1 1, 4 1, 4 4, 1 4, 1 1))'))) -- L-shaped remainder after subtracting overlapping square (WKT vertex order may vary)
;