SQL & PL/SQL

When I run this:

update hrs.pays_history
set pays_history.distribution_group
(SELECT EMPLOYEE_DISTRIBUTIONS.DISTRIBUTION_GROUP, 
EMPLOYEE_MASTER.EMPLOYEE_NO,
EMPLOYEE_DISTRIBUTIONS.ACCOUNT_ID, 
PAYS_HISTORY.DISTRIBUTION_GROUP, 
ACCOUNT_HISTORY.ACCOUNT_ID, ACCOUNT_HISTORY.CHECK_KEY *
FROM HRS.ACCOUNT_HISTORY ACCOUNT_HISTORY, 
HRS.EMPLOYEE_DISTRIBUTIONS EMPLOYEE_DISTRIBUTIONS, 
HRS.EMPLOYEE_MASTER EMPLOYEE_MASTER, 
HRS.PAYS_HISTORY PAYS_HISTORY
WHERE EMPLOYEE_DISTRIBUTIONS.EMPLOYEE_NO = EMPLOYEE_MASTER.EMPLOYEE_NO AND 
PAYS_HISTORY.EMPLOYEE_NO = EMPLOYEE_MASTER.EMPLOYEE_NO AND 
ACCOUNT_HISTORY.CHECK_KEY = PAYS_HISTORY.CHECK_KEY AND 
((PAYS_HISTORY.CONTRACT_YEAR = 2008) AND 
(ACCOUNT_HISTORY.TRANSACTION_TYPE = 'GRS')
AND EMPLOYEE_DISTRIBUTION.ACCOUNT_ID = ACCOUNT_HISTORY.ACCOUNT_ID)
[pre/]

I get the message missing equal sign, but I can see where its missing.

Thanks