Categories:: Geospatial Functions

ST_COVERS¶

This returns TRUE if no point in one geospatial object is outside of another geospatial object. In other words:

GEOGRAPHY object g2 is outside GEOGRAPHY object g1.
GEOMETRY object g2 is outside GEOMETRY object g1.

ST_COVERS is similar to, but subtly different from, ST_CONTAINS. For details on the differences between “covers” and “contains”, see the Dimensionally Extended 9-Intersection Model (DE-9IM).

Although ST_COVERS and ST_CONTAINS might seem similar, the two functions have subtle differences. For details on the differences between “covers” and “contains”, see the Dimensionally Extended 9-Intersection Model (DE-9IM).

Note

This function does not support using a GeometryCollection or FeatureCollection as input values.

See also:: ST_CONTAINS , ST_COVEREDBY

Syntax¶

ST_COVERS( <geography_expression_1> , <geography_expression_2> )

ST_COVERS( <geometry_expression_1> , <geometry_expression_2> )

Arguments¶

geography_expression_1: A GEOGRAPHY object that is not a GeometryCollection or FeatureCollection.
geography_expression_2: A GEOGRAPHY object that is not a GeometryCollection or FeatureCollection.
geometry_expression_1: A GEOMETRY object that is not a GeometryCollection or FeatureCollection.
geometry_expression_2: A GEOMETRY object that is not a GeometryCollection or FeatureCollection.

Returns¶

BOOLEAN.

Usage Notes¶

For GEOMETRY objects, the function reports an error if the two input GEOMETRY objects have different SRIDs.

Examples¶

GEOGRAPHY Examples¶

This shows a simple use of the ST_COVERS function:

create table geospatial_table_01 (g1 GEOGRAPHY, g2 GEOGRAPHY);
insert into geospatial_table_01 (g1, g2) values 
    ('POLYGON((0 0, 3 0, 3 3, 0 3, 0 0))', 'POLYGON((1 1, 2 1, 2 2, 1 2, 1 1))');

SELECT ST_COVERS(g1, g2) 
    FROM geospatial_table_01;
+-------------------+
| ST_COVERS(G1, G2) |
|-------------------|
| True              |
+-------------------+

GEOMETRY Examples¶

The query below shows several examples of using ST_COVERS. Note how the Polygon covers (but does not contain) a LineString on its border.

SELECT ST_COVERS(poly, poly_inside),
       ST_COVERS(poly, poly),
       ST_COVERS(poly, line_on_boundary),
       ST_COVERS(poly, line_inside)
  FROM (SELECT TO_GEOMETRY('POLYGON((-2 0, 0 2, 2 0, -2 0))') AS poly,
               TO_GEOMETRY('POLYGON((-1 0, 0 1, 1 0, -1 0))') AS poly_inside,
               TO_GEOMETRY('LINESTRING(-1 1, 0 2, 1 1)') AS line_on_boundary,
               TO_GEOMETRY('LINESTRING(-2 0, 0 0, 0 1)') AS line_inside);

+------------------------------+----------------------+----------------------------------+-----------------------------+
| ST_COVERS(POLY, POLY_INSIDE) | ST_COVERS(POLY,POLY) | ST_COVERS(POLY,LINE_ON_BOUNDARY) | ST_COVERS(POLY,LINE_INSIDE) |
|------------------------------+----------------------+----------------------------------+-----------------------------|
| True                         | True                 | True                             | True                        |
+------------------------------+----------------------+----------------------------------+-----------------------------+