Stored Procedure With Function giving me errors in Oracle - function

Question

I have stored procedure and function and I am calling the function in the stored procedure in ORACLE.The function CalculateIncomeTax is what is giving me errors.In MSSQL,this type of update is possible because I have done it before.I called the function in the stored procedure.When I read around the answer I get is to use a package before I cannot use a function to update a table from another table.Please if you have any idea,tell me.The error I get is
table string.string is mutating, trigger/function may not see it
Cause: A trigger (or a user defined plsql function that is referenced in this statement) attempted to look at (or modify) a table that was in the middle of being modified by the statement which fired it.
Action: Rewrite the trigger (or function) so it does not read that table.
This is function
CREATE OR REPLACE function CalculateIncomeTax(periodId NVARCHAR2,
employeeId NVARCHAR2, taxableIncome NUMBER)return NUMBER
AS
IncomeTax NUMBER (18,4);Taxable NUMBER(18,4);
BEGIN
SELECT SUM(CASE WHEN (taxableIncome > T.TAX_CUMMULATIVE_AMOUNT)
THEN (taxableIncome - T.TAX_CUMMULATIVE_AMOUNT)* T.TAX_PERCENTAGE/ 100
ELSE 0.00 END ) INTO IncomeTax
FROM TAX_LAW T JOIN PAY_GROUP P ON P.PAY_FORMULA_ID =T.TAX_FORMULA_ID
JOIN PAYROLL_MASTER PP ON P.PAY_CODE =PP.PAY_PAY_GROUP_CODE
WHERE PP.PAY_EMPLOYEE_ID = employeeId AND PP.PAY_PERIOD_CODE = periodId;
if IncomeTax IS NULL THEN IncomeTax :=0;
end if;
return IncomeTax;
end;/
This is the stored procedure
CREATE OR REPLACE PROCEDURE PROCESSPAYROLLMASTER (periodcode
VARCHAR2) AS BEGIN
INSERT INTO PAYROLL_MASTER
(
PAY_PAYROLL_ID,PAY_EMPLOYEE_ID ,PAY_EMPLOYEE_NAME,PAY_SALARY_GRADE_CODE
,PAY_SALARY_NOTCH_CODE,PAY_BASIC_SALARY,PAY_TOTAL_ALLOWANCE
,PAY_TOTAL_CASH_BENEFIT,PAY_MEDICAL_BENEFIT,PAY_TOTAL_BENEFIT
,PAY_TOTAL_DEDUCTION,PAY_GROSS_SALARY,PAY_TOTAL_TAXABLE,PAY_INCOME_TAX
,PAY_TAXABLE,PAY_PERIOD_CODE,PAY_BANK_CODE,PAY_BANK_NAME,PAY_BANK_ACCOUNT_NO
,PAY_PAY_GROUP_CODE )
SELECT
1,
E.EMP_ID AS PAY_EMPLOYEE_ID ,
E.EMP_FIRST_NAME || ' ' || E.EMP_LAST_NAME AS PAY_EMPLOYEE_NAME,
E.EMP_RANK_CODE,
'CODE',
(SC.SAL_MINIMUM_AMOUNT+( SN.SAL_SALARY_PERCENTAGE *
SC.SAL_MINIMUM_AMOUNT)/100) AS PAY_BASIC_SALARY,
0,
0,
0,
0,
0,
0,
0,
0,
0,
periodcode,
'BANKCODE',
'BANKNAME',
'BANKNUMBER',
'GENERAL'
FROM EMPLOYEE E
LEFT JOIN SALARY_SCALE SC ON SC.SAL_RANK_CODE = E.EMP_RANK_CODE
LEFT JOIN SALARY_NOTCH SN ON SC.SAL_ID = SN.SAL_SALARYSCALE_ID
WHERE E.EMP_RANK_CODE = SC.SAL_RANK_CODE AND E.EMP_STATUS=2;
CALCULATEALLOWANCE(v_payrollId,periodcode);
CALCULATECASHBENEFITS(v_payrollId,periodcode);
CALCULATEDEDUCTIONS(v_payrollId,periodcode);
-- UPDATE PAYROLL PAY_INCOME_TAX
UPDATE PAYROLL_MASTER PM SET PM.PAY_INCOME_TAX = CalculateIncomeTax(PM.PAY_PERIOD_CODE,PM.PAY_EMPLOYEE_ID,PM.PAY_TOTAL_TAXABLE) WHERE PM.PAY_PAYROLL_ID = v_payrollId;
UPDATE PAYROLL_PROCESS set PAY_CANCELLED = 1 WHERE PAY_PAY_GROUP_CODE='GENERAL' AND PAY_PERIOD_CODE=periodcode
AND PAY_ID<>v_payrollId;
COMMIT;
END ;
/

Answer 1

The function is querying the same table you are updating, which is what the error is reporting. As it happens you are not changing the value of the column you're querying, but Oracle doesn't check to that level - not least because there could be, for instance, a trigger that has less obvious side-effects.
The best solution really would be to not have to update at all, and to calculate and set all the value as part of the original insert, by joining to all the relevant tables. But you are already calling other procedures which are, presumably, updating some of the values you're inserting as zeros, including pay_total_taxable.
Unless you're able to reevaluate those as well, you may be stuck with doing a further update. In which case, you could remove the reference to the payroll_master table from the function and instead pass in the relevant data.
I think this is equivalent, though with out the table structures, sample data and what the other procedures are doing it's hard to be sure (so this is untested, obviously):
create or replace function calculateincometax (
p_periodid nvarchar2,
p_employeeid nvarchar2,
p_paypaygroupcode payroll_master.pay_pay_group_code%type,
p_taxableincome number
) return number as
l_incometax number(18, 4);
begin
select coalesce(sum(case when p_taxableincome > t.tax_cummulative_amount
then (taxableincome - t.tax_cummulative_amount) * t.tax_percentage / 100
else 0 end), 0)
into l_incometax
from tax_law t
join pay_group p
on p.pay_formula_id = t.tax_formula_id
where p.pay_code = p_paypaygroupcode;
return l_incometax;
end;
/
and then include the extra argument in your call:
update payroll_master pm
set pm.pay_income_tax = calculateincometax(pm.pay_period_code, pm.pay_employee_id,
pm.pay_pay_group_code, pm.pay_total_taxable)
where pm.pay_payroll_id = v_payrollid;
Although v_payrollid isn't defined in what you've shown, so even that isn't entirely clear.
I've also modified the function argument and local variable names with prefixes to remove potential ambiguity (which you seem to do by removing underscores from the names), removed the unused variable, and added a coalesce() call in place of the separate null check. Those things aren't directly relevant to the approach though.