ST_UNION()

All functions > GEOSPATIAL > ST_UNION()

Returns the geometry/geography representing the point set union of two inputs.

Signatures

Union

Returns: Union; sub kind depends on merged shape

ST_UNION(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:

• Merges two geometries into one, dissolving shared boundaries
• On Trino: transpiled to geometry_union()
• Both inputs must be the same type family
• Returns NULL if either input is NULL

Examples

SELECT
    f1 := ST_ASTEXT(ST_UNION(ST_GEOMFROMTEXT('POLYGON ((0 0, 2 0, 2 2, 0 2, 0 0))'), ST_GEOMFROMTEXT('POLYGON ((1 0, 3 0, 3 2, 1 2, 1 0))'))) -- Union of two adjacent rectangles (WKT vertex order may vary)
;