## Name

ST_CoveredBy — Tests if every point of A lies in B

## Synopsis

`boolean ST_CoveredBy(`geometry geomA, geometry geomB`)`;

`boolean ST_CoveredBy(`geography geogA, geography geogB`)`;

## Descrizione

Returns `true` if every point in Geometry/Geography A lies inside (i.e. intersects the interior or boundary of) Geometry/Geography B. Equivalently, tests that no point of A lies outside (in the exterior of) B.

In mathematical terms: ST_CoveredBy(A, B) ⇔ A ⋂ B = A

ST_CoveredBy is the converse of ST_Covers. So, `ST_CoveredBy(A,B) = ST_Covers(B,A)`.

Generally this function should be used instead of ST_Within, since it has a simpler definition which does not have the quirk that "boundaries are not within their geometry".

 Questa funzione incorpora l'uso di una comparazione tra i bounding box in modo da usare qualunque indice spaziale disponibile sulle geometrie. To avoid index use, use the function `_ST_CoveredBy`.
 Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`
 Do not use this function with invalid geometries. You will get unexpected results.

Eseguito dal modulo GEOS

Availability: 1.2.2

NOTE: this is the "allowable" version that returns a boolean, not an integer.

Not an OGC standard, but Oracle has it too.

## Esempi

```--a circle coveredby a circle
SELECT ST_CoveredBy(smallc,smallc) As smallinsmall,
ST_CoveredBy(smallc, bigc) As smallcoveredbybig,
ST_CoveredBy(ST_ExteriorRing(bigc), bigc) As exteriorcoveredbybig,
ST_Within(ST_ExteriorRing(bigc),bigc) As exeriorwithinbig
FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;
--Result
smallinsmall | smallcoveredbybig | exteriorcoveredbybig | exeriorwithinbig
--------------+-------------------+----------------------+------------------
t            | t                 | t                    | f
(1 row) ```