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    ApsaraDB RDS:ST_Collect

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    ApsaraDB RDS:ST_Collect

    Last Updated:Mar 28, 2026

    Collects geometry objects into a MULTI\* or GeometryCollection, depending on whether the input geometries share the same type (homogeneous) or have different types (heterogeneous).

    Syntax

    geometry ST_Collect(geometry g1, geometry g2);
geometry ST_Collect(geometry[] g1Array);
geometry ST_Collect(geometry set g1Field);

    Parameters

    ParameterDescription
    g1The first geometry object.
    g2The second geometry object.
    g1ArrayAn array of geometry objects.
    g1FieldA field of geometry objects from a dataset, used when calling ST_Collect as an aggregate function.

    Usage notes

    ST_Collect has three variants:

    • Variant 1 — two-input (g1, g2): Combines two geometry objects. Returns a MULTI\* type if both inputs share the same geometry type, or a GeometryCollection if the types differ.

    • Variant 2 — array (g1Array): Combines an array of geometry objects into a single collection.

    • Variant 3 — aggregate (g1Field): Acts as an aggregate function, collecting all geometry objects from a rowset into a single geometry.

    ST_Collect supports CircularString and Curve objects, but may not return the expected MultiCurve or MULTI\* type in all cases.

    If any input is itself a collection type (MULTI\* or GeometryCollection), ST_Collect returns a GeometryCollection rather than a flat MULTI\* type. To prevent this, use ST_Dump in a subquery to expand the input collections to their atomic elements before calling ST_Collect.

    ST_Collect vs. ST_Union

    Both functions combine geometry objects, but behave differently:

    BehaviorST_CollectST_Union
    Dissolves boundariesNoYes
    LineString handlingReturns a MultiLineStringSplits at node intersections
    Return typeMULTI\* or GeometryCollectionMay return a simple geometry
    PerformanceFasterSlower

    Use ST_Collect to group geometries without merging their boundaries. Use ST_Union when you need the geometries dissolved into a single unified geometry.

    Examples

    Variant 1: Two-input

    Collect two points of the same type — returns a MULTIPOINT:

    SELECT ST_AsText(ST_Collect('POINT(0 0)'::geometry, 'POINT(0 1)'::geometry));

    Result:

          st_astext
---------------------
 MULTIPOINT(0 0,0 1)
(1 row)

    Collect geometries of different types — returns a GeometryCollection:

    SELECT ST_AsText(ST_Collect('POINT(0 0)'::geometry, 'LINESTRING(0 2,0 3)'::geometry));

    Result:

                         st_astext
----------------------------------------------------
 GEOMETRYCOLLECTION(POINT(0 0),LINESTRING(0 2,0 3))
(1 row)

    Variant 3: Aggregate

    Collect all points from a subquery into a single MULTIPOINT:

    SELECT ST_AsText(ST_Collect(t.geom))
FROM (
  SELECT (ST_DumpPoints(st_buffer('POINT(0 0)'::geometry, 1, 'quad_segs=2'))).geom AS geom
) AS t;

    Result:

                                   st_astext
----------------------------------------------------------------
 MULTIPOINT(1 0,0.707106781186548 -0.707106781186547,0 -1,-0.70
 7106781186546 -0.707106781186549,-1 0,-0.70710678118655 0.70710
 6781186545,0 1,0.707106781186544 0.707106781186551,1 0)
(1 row)

    See also