MBRCoveredBy(g1,g2)

Returns 1 or 0 to indicate whether the minimum bounding rectangle of g1
is covered by the minimum bounding rectangle of g2. This tests the
opposite relationship as MBRCovers().

MBRCoveredBy() and MBRCovers() handle their arguments and return a
value as follows:

o Return NULL if either argument is NULL or an empty geometry

o Return ER_GIS_INVALID_DATA if either argument is not a valid geometry
  byte string (SRID plus WKB value)

o Otherwise, return non-NULL

URL: http://dev.mysql.com/doc/refman/5.7/en/spatial-relation-functions-mysql-specific.html

