calculating the sum of a field in a query with join

Select attend.overtimehours from attendance attend, salarydetail sal where attend.employeeid = sal.employeeid

in the above query,how can i fetch the sum of overtimehours?
attendance table
column_name data_type
-------------------- -------------------
attendancerid number
employeeid number
shiftid number
dayofattendance date
timein date
timeout date
numberofhours number
overtimehours number
presentflag varchar2

salarydetail table
column_name data_type
----------------- --------------------
salaryid number
employeeid number
startdate date
enddate date
grosssalary number
netsalary number
overtimeamount number
lopamount number
paiddays number

please post both of your tables structures for further details.

If you need only sum of overtime hours then the following query works for u

Select employeeid,sum(overtimehours )
from attendance
group by employeeid

If u want bothe sum of overtime and overtime amount then use the following query,

Select attend.employeeid, sum(attend.overtimehours),sum(sal.overtimeamount)
from attendance attend, salarydetail sal
where attend.employeeid = sal.employeeid
group by attend.employeeid