MBRCovers(g1, g2)

Returns 1 or 0 to indicate whether the minimum bounding rectangle of g1
covers the minimum bounding rectangle of g2. This tests the opposite
relationship as MBRCoveredBy(). See the description of MBRCoveredBy()
for examples.

MBRCovers() handles its arguments as follows:

o If either argument is NULL or an empty geometry, the return value is
  NULL.

o If either argument is not a syntactically well-formed geometry byte
  string, an ER_GIS_INVALID_DATA error occurs.

o Otherwise, the return value is non-NULL.

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

