3.9 KiB
| sidebar_label | title | toc_max_heading_level |
|---|---|---|
| Geometry Functions | Geometry Functions | 4 |
Geometry Input Functions
Geometry input functions create geometry data from WTK.
ST_GeomFromText
ST_GeomFromText(VARCHAR WKT expr)
Description: Return a specified GEOMETRY value from Well-Known Text representation (WKT).
Return value type: GEOMETRY
Applicable data types: VARCHAR
Applicable table types: standard tables and supertables
Explanations：
- The input can be one of WTK string, like POINT, LINESTRING, POLYGON, MULTIPOINT, MULTILINESTRING, MULTIPOLYGON, GEOMETRYCOLLECTION.
- The output is a GEOMETRY data type, internal defined as binary string.
Geometry Output Functions
Geometry output functions convert geometry data into WTK.
ST_AsText
ST_AsText(GEOMETRY geom)
Description: Return a specified Well-Known Text representation (WKT) value from GEOMETRY data.
Return value type: VARCHAR
Applicable data types: GEOMETRY
Applicable table types: standard tables and supertables
Explanations：
- The output can be one of WTK string, like POINT, LINESTRING, POLYGON, MULTIPOINT, MULTILINESTRING, MULTIPOLYGON, GEOMETRYCOLLECTION.
Geometry Relationships Functions
Geometry relationships functions determine spatial relationships between geometries.
ST_Intersects
ST_Intersects(GEOMETRY geomA, GEOMETRY geomB)
Description: Compares two geometries and returns true if they intersect.
Return value type: BOOL
Applicable data types: GEOMETRY, GEOMETRY
Applicable table types: standard tables and supertables
Explanations：
- Geometries intersect if they have any point in common.
ST_Equals
ST_Equals(GEOMETRY geomA, GEOMETRY geomB)
Description: Returns TRUE if the given geometries are "spatially equal".
Return value type: BOOL
Applicable data types: GEOMETRY, GEOMETRY
Applicable table types: standard tables and supertables
Explanations：
- 'Spatially equal' means ST_Contains(A,B) = true and ST_Contains(B,A) = true, and the ordering of points can be different but represent the same geometry structure.
ST_Touches
ST_Touches(GEOMETRY geomA, GEOMETRY geomB)
Description: Returns TRUE if A and B intersect, but their interiors do not intersect.
Return value type: BOOL
Applicable data types: GEOMETRY, GEOMETRY
Applicable table types: standard tables and supertables
Explanations：
- A and B have at least one point in common, and the common points lie in at least one boundary.
- For Point/Point inputs the relationship is always FALSE, since points do not have a boundary.
ST_Covers
ST_Covers(GEOMETRY geomA, GEOMETRY geomB)
Description: Returns TRUE if every point in Geometry B lies inside (intersects the interior or boundary of) Geometry A.
Return value type: BOOL
Applicable data types: GEOMETRY, GEOMETRY
Applicable table types: standard tables and supertables
Explanations：
- A covers B means no point of B lies outside (in the exterior of) A.
ST_Contains
ST_Contains(GEOMETRY geomA, GEOMETRY geomB)
Description: Returns TRUE if geometry A contains geometry B.
Return value type: BOOL
Applicable data types: GEOMETRY, GEOMETRY
Applicable table types: standard tables and supertables
Explanations：
- A contains B if and only if all points of B lie inside (i.e. in the interior or boundary of) A (or equivalently, no points of B lie in the exterior of A), and the interiors of A and B have at least one point in common.
ST_ContainsProperly
ST_ContainsProperly(GEOMETRY geomA, GEOMETRY geomB)
Description: Returns TRUE if every point of B lies inside A.
Return value type: BOOL
Applicable data types: GEOMETRY, GEOMETRY
Applicable table types: standard tables and supertables
Explanations：
- There is no point of B lies in the the boundary or exterior of A.