The ST_Covers method tests if the geometry-expression completely covers geo2. geometry-expression.ST_Covers( geo2 ) is equivalent to geo2.ST_CoveredBy( geometry-expression ).
This predicate is similar to ST_Contains except for one subtle difference. The ST_Contains predicate requires that one or
more interior points of geo2 lie in the interior of the geometry-expression. For ST_Covers(), the method returns 1 if no point of geo2 lies outside of the geometry-expression. Also, ST_Covers can be used with geometries in round-Earth spatial reference systems, while ST_Contains can not.
If the geometry-expression contains circularstrings, then these are interpolated to line strings.
The following example lists the ShapeIDs where the given polygon covers each Shape geometry. This example returns the result
1,16,17,19,26. Note that ShapeID 1 is listed even though the polygon intersects that row's Shape point only at the polygon's boundary.
SELECT LIST( ShapeID ORDER BY ShapeID )
WHERE NEW ST_Polygon( NEW ST_Point( 0, 0 ),
NEW ST_Point( 8, 2 ) ).ST_Covers( Shape ) = 1