Pfthb

WITH Employee AS
 ( SELECT E.Com_Id,
 Com.Sinl_ID CLASS.Details_ID,
 Employee E
 INNER JOIN employee_Det Det ON E.Com_ID=Det.Com_ID
 INNER JOIN Employee_Sig Sig ON E.Com_ID=Sig.Main_Com_ID
 INNER JOIN Emp_Sig_Det Com Sig.Com_ID=Com.Com_ID
 INNER JOIN Employee_Class CLASS ON Com.F_ID=Class.Class_Id 
 ******N*******
 INNER JOIN Employee_AB_Class ABC ON E.Com_ID=AB.Main_Com_Id
 INNER JOIN Emp_AB_Class_Sig ABC_Sig ON AB.COM_ID=ABC_SIG.COM_ID
 INNER JOIN Employee_Class Class1 ABC_Sig.F_ID=Class1.Class_Id
 WHERE Det.ODate='2015-01-01'
 AND Sig.ODate='2015-01-01'
 AND Com.ODate='2015-01-01'
 AND Class.ODate='2015-01-01'
 AND Abc.ODate='2015-01-01'
 AND ABC_Sig.ODate='2015-01-01'
 AND Class.ODate='2015-01-01'
 AND ),
 DEPT AS
 ( SELECT E.Com_Id,
 Com.Sinl_ID CLASS.Details_ID,
 DEPT E
 INNER JOIN DEPT_Det Det ON E.Com_ID=Det.Com_ID
 INNER JOIN DEPT_Sig Sig ON E.Com_ID=Sig.Main_Com_ID
 INNER JOIN DEPT_Sig_Det Com Sig.Com_ID=Com.Com_ID
 INNER JOIN DEPT_Class CLASS ON Com.F_ID=Class.Class_Id 
 ******N*******
 INNER JOIN DEPT_AB_Class ABC ON E.Com_ID=AB.Main_Com_Id
 INNER JOIN DEPT_AB_Class_Sig ABC_Sig ON AB.COM_ID=ABC_SIG.COM_ID
 INNER JOIN DEPT_Class Class1 ABC_Sig.F_ID=Class1.Class_Id
 WHERE Det.ODate='2015-01-01'
 AND Sig.ODate='2015-01-01'
 AND Com.Date='2015-01-01'
 AND Class.ODate='2015-01-01'
 AND Abc.ODate='2015-01-01'
 AND ABC_Sig.ODate='2015-01-01'
 AND Class.ODate='2015-01-01'
 AND ),
SELECT *
FROM Employee
UNION ALL
SELECT *
FROM DEPT;

Counts of the following Tables are too huge to be processed in
Hive, Can you please, provide an hint how to increase the performance

Employee Counts

Det - 15 Million 
Sig - 15 Million
Com - 10 Million
Class - 10 Million
Abc.ODate - 1000 Records
ABC_Sig -10 Million
Class.ODate- 10 Million

Dept Counts

Det - 25 Million 
Sig - 25 Million
Com -20 Million
Class - 20 Million
Abc.ODate - 1000 Records
ABC_Sig -50 Million
Class - 50 Million