ST_Within — Tests if no points of A lie in the exterior of B, and A and B have at least one interior point in common.
Returns TRUE if geometry A is completely inside geometry B. For this function to make sense, the source geometries must both be of the same coordinate projection, having the same SRID. It is a given that if ST_Within(A,B) is true and ST_Within(B,A) is true, then the two geometries are considered spatially equal.
A subtlety of this definition is that the boundary of a geometry is not within the geometry. This means that lines and points lying in the boundary of a polygon or line are not within the geometry. For further details see Subtleties of OGC Covers, Contains, Within. (The ST_CoveredBy predicate provides a more inclusive relationship).
ST_Within is the inverse of ST_Contains.
ST_Within(A,B) = ST_Contains(B,A).
This function automatically includes a bounding box comparison
that makes use of any spatial indexes that are available on the geometries.
To avoid index use, use the function
Performed by the GEOS module
Enhanced: 2.3.0 Enhancement to PIP short-circuit for geometry extended to support MultiPoints with few points. Prior versions only supported point in polygon.
Enhanced: 3.0.0 enabled support for
Do not use this function with invalid geometries. You will get unexpected results.
NOTE: this is the "allowable" version that returns a boolean, not an integer.
This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s18.104.22.168 // s22.214.171.124 - a.Relate(b, 'T*F**F***')
This method implements the SQL/MM specification. SQL-MM 3: 5.1.30
--a circle within a circle SELECT ST_Within(smallc,smallc) As smallinsmall, ST_Within(smallc, bigc) As smallinbig, ST_Within(bigc,smallc) As biginsmall, ST_Within(ST_Union(smallc, bigc), bigc) as unioninbig, ST_Within(bigc, ST_Union(smallc, bigc)) as biginunion, ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion FROM ( SELECT ST_Buffer(ST_GeomFromText('POINT(50 50)'), 20) As smallc, ST_Buffer(ST_GeomFromText('POINT(50 50)'), 40) As bigc) As foo; --Result smallinsmall | smallinbig | biginsmall | unioninbig | biginunion | bigisunion --------------+------------+------------+------------+------------+------------ t | t | f | t | t | t (1 row)