I had problem with update

Question

hi experts,
i am playing with parameterizsed cursor, so i did the following thing.
it's working. if give empid it retrives the emmployee is belongs which department.
CREATE OR REPLACE FUNCTION FUNC_SOMETHING_EMPLOYEE(EMPID VARCHAR2)
RETURN VARCHAR2 IS
RES VARCHAR2(200);
CURSOR C1 IS SELECT * FROM EMPLOYEES WHERE EMPLOYEE_ID=EMPID;
CURSOR C2(DID NUMBER) IS SELECT * FROM DEPARTMENTS WHERE DEPARTMENT_ID = DID;
BEGIN
FOR CR1 IN C1
LOOP
FOR CR2 IN C2(CR1.DEPARTMENT_ID)
LOOP
RES := 'EMPLOYEE ID : ' ||CR1.EMPLOYEE_ID|| 'DEPARTMENT NAME : '||cr2.DEPARTMENT_NAME;
END LOOP;
END LOOP;
RETURN RES;
END;
/but i want update the sal of particular employee:
but some error throws.
SQL> ed
Wrote file afiedt.buf
  1  CREATE OR REPLACE FUNCTION FUNC_SOMETHING_EMPLOYEE(EMPID VARCHAR2 , amt number)
  2  RETURN VARCHAR2 IS
  3  RES VARCHAR2(200);
  4  CURSOR C1 IS SELECT * FROM EMPLOYEES WHERE EMPLOYEE_ID=EMPID;
  5  CURSOR C2(DID NUMBER) IS SELECT * FROM DEPARTMENTS WHERE DEPARTMENT_ID = DID;
  6  BEGIN
  7  FOR CR1 IN C1
  8  LOOP
  9  FOR CR2 IN C2(CR1.DEPARTMENT_ID)
10  LOOP
11  update EMPLOYEES set salary = cr1.salary*amt where EMPLOYEE_ID = cr1.EMPLOYEE_ID ;
12  RES := cr1.salary;
13  END LOOP;
14  END LOOP;
15  RETURN RES;
16* END;
SQL> /
Function created.
SQL> select FUNC_SOMETHING_EMPLOYEE('1981',22) from dual;
select FUNC_SOMETHING_EMPLOYEE('1981',22) from dual
ERROR at line 1:
ORA-14551: cannot perform a DML operation inside a query
ORA-06512: at "HR.FUNC_SOMETHING_EMPLOYEE", line 11can any one explain what is happening.?
oracle db10g
sorry peoples while pasting matching condition left out,.

Answer 1

I think I see your confusion.
There are two different languages involved here, SQL and PL/SQL.
The SQL language is a non-procedural language whose role is to define data structures (DDL) and manipulate data (DML). The language also contains transaction control statements ( commit, rollback, savepoint) and some other constructions that aren't able to be categorised so neatly, but which can be ignored for now.
The PL/SQL language is a complete procedural language (that's the PL bit of the name) which is based on the ADA language, and supports the SQL language within it.
You can write PL/SQL packages, procedures and functions which contain no SQL at all if you wish.
The power of PL/SQL though is the way that it integrates SQL within it.
In your example you have written a PL/SQL function which updates some data using a SQL statement. You can call that function from other PL/SQL procedures and functions - you showed an example calling it from a PL/SQL anonymous block, and it ran just fine.
You can also use a PL/SQL function (but not a procedure) within a SQL statement, but there are restrictions on what the function is allowed to do in this context. In particular, as you've found out, no updates! These are just "the rules" and they are documented in detail.
Don't be offended when people write "thats a doc question" and give a reference, because that document contains the facts stated better and more completely than could be written here. It's much better to read the documentation that some explanation written here that is only partially correct (I have written some of those myself).
There are other questions where the answers are not so clear cut, and that is where you may see different responses. They will reflect the writers background and experience ... neither right nor wrong, just different approaches to situations.
So read a lot, try things out, and then ask lots of questions about things that you are unsure about.
Dave