Impact of NULL values on where-clause/group-by-clause in Hive queries

Following is the check to verified that NULL values do not impact GROUP BY but it DOES IMPACT where clause.

Query: select count(*) from table1 where (field1 is NULL) AND dth >= '2014-12-01-00' AND dth <= '2014-12-01-23';
Result: 24

- select count(*) from table1 where (field1 != 'Value1') AND dth >= '2014-12-01-00' AND dth <= '2014-12-01-23';
Result: 1853517 (The correct count is 1853541 which gets reported incorrectly here because count of NULL values is ignored.)

- select count(*) from table1 where (field1 = 'Value1') AND dth >= '2014-12-01-00' AND dth <= '2014-12-01-23'
Result: 142570

select field1, count(*) from table1 where dth >= '2014-12-01-00' AND dth <= '2014-12-01-23' GROUP by field1;
Result:

field1	_c1
ValidateAuthorization	1196966
GetUserProfile	470557
Authorize	142570
SignIn	86351
	26101
Register	14726
GetUserEntitlement	12056
UpdateUser	11529
GetChildApprovalStatus	9813
UserProfile	9362
LogOut	4974
LogOn	3763
GetExtendedProfile	3060
GetAvaiableTrials	1934
LinkAccounts	1011
UpdateProfile	387
ChangePassword	337
SignUpChild	206
UploadProfilePicture	173
CoppaSentinelValidate	80
GetChildrenForModerator	38
GetModeratorsForChild	37
NULL	24
UpdateUserType	16
LdapSignIn	14
ModeratorApproval	13
UpdateChildModeratorAccountStatus	12
SignUp	1