| <!-- |
| Licensed to the Apache Software Foundation (ASF) under one |
| or more contributor license agreements. See the NOTICE file |
| distributed with this work for additional information |
| regarding copyright ownership. The ASF licenses this file |
| to you under the Apache License, Version 2.0 (the |
| "License"); you may not use this file except in compliance |
| with the License. You may obtain a copy of the License at |
| |
| http://www.apache.org/licenses/LICENSE-2.0 |
| |
| Unless required by applicable law or agreed to in writing, |
| software distributed under the License is distributed on an |
| "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| KIND, either express or implied. See the License for the |
| specific language governing permissions and limitations |
| under the License. |
| --> |
| |
| # ST_Collect_Agg |
| |
| Introduction: Collects all non-null spatial values in a group without dissolving their |
| boundaries. Homogeneous `Point`, `LineString`, or `Polygon` values produce the corresponding |
| multi-object; mixed types produce a `GeometryCollection`. |
| |
|  |
| |
| Format: |
| |
| `ST_Collect_Agg (A: Geometry)` |
| |
| `ST_Collect_Agg (A: Geography)` |
| |
| Return type: `Geometry` or `Geography`, matching the input type |
| |
| Since: `v1.9.1` |
| |
| Null values are ignored and duplicates are preserved. The function returns `NULL` when a group |
| has no non-null values. All `Geography` values in a group must have the same SRID. |
| |
| `ST_Collect_Aggr` is also registered as an alias. |
| |
| Geometry example: |
| |
| ```sql |
| SELECT ST_Collect_Agg(geom) |
| FROM ( |
| VALUES |
| (ST_GeomFromWKT('POINT(1 2)')), |
| (ST_GeomFromWKT('POINT(3 4)')), |
| (ST_GeomFromWKT('POINT(1 2)')) |
| ) AS observations(geom) |
| ``` |
| |
| Output: |
| |
| ``` |
| MULTIPOINT ((1 2), (3 4), (1 2)) |
| ``` |
| |
| Geography example: |
| |
| ```sql |
| SELECT region, ST_Collect_Agg(geog) AS geographies |
| FROM observations |
| GROUP BY region |
| ``` |
