Retirement Date Function in Oracle SQL - sql

Question

Please I want to calculate the retirement of an employee from his Date of First Appointment using a function before retrieving the result using a trigger and store it in the Retirement date column: but I am not good with the syntax please can someone help:... Below is my code for the function
CREATE OR REPLACE Function EDOR_DATE
(DOFA IN date)
RETURN date
IS
NEW_EDOR_RESULT date;
BEGIN
SELECT DOFA + ((365*35) + 9) as NEW_EDOR
FROM EMPLOYEES_MASTER_DETAILS;
fetch NEW_EDOR into NEW_EDOR_RESULT;
RETURN NEW_EDOR_RESULT;
END;

Answer 1

First a couple comments on the changes you indicated you made to the function:
Removing the "IN" from the declaration actually accomplishes nothing.
If you do not specify "IN', "OUT", or "IN OUT" the compiler defaults to "IN". All removing it does is a change from an explicit to implicit declaration.
Placing a semi-colon (;) where indicated will generate an error.
As for the function itself you are making it way more complicated than necessary. A simple assignment is all that's needed. Also, Boneist's suggestion of add_months is the correct function for adding years as it will adjust for leap year and number of days per month (if needed).
Thus your function reduces to:
create or replace function edor_date(dofa in date)
return date
is
l_edor_date date;
begin
l_edor_date := add_months(dofa, 35*12) ;
return l_edor_date ;
end;
or even further to just:
create or replace function edor_date (dofa in date)
return date
is
begin
return add_months(dofa, 35*12) ;
end;
BTW: I actually like the idea of using a function for this as it hides the implementation details of the business rule. However, it does impose a slight overhead for each call.

Answer 2

CREATE OR REPLACE Function EDOR_DATE
(DOFA date)
RETURN date
IS
NEW_EDOR_RESULT date;
BEGIN
--I am converting this to a case statement that is easier to read
select
case
when dofa - dob <= 25 then dofa + ((365*35)+9)
else dob + ((365*60)+9)
end
into new_edor_result
from employees_master_details;
return new_edor_result;
end;

Answer 3

This can be done without needing to use a function. Also, why are you adding numbers of days? A year is not 365 days long. You should be using the add_months() feature.
Here is how I would do this, assuming all the columns in question belong to the EMPLOYEES_MASTER_DETAILS table:
select emp_id,
dob,
hire_date,
case when months_between(hire_date, dob) <= 25 * 12 then add_months(hire_date, 35*12)
else add_months(dob, 60*12)
end retirement_date
from EMPLOYEES_MASTER_DETAILS emd;
If you need to calculate the retirement upon insert, then simply use the case expression as part of the insert statement.