plsql - Call a stored procedure in a trigger PL/SQL

Question

Well I'm trying to call a stored procedure in my trigger.

The error I'm getting

"table %s.%s 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 my code of the trigger:

create or replace TRIGGER check_salary_trg 
AFTER INSERT OR UPDATE ON employees
FOR EACH ROW

BEGIN 
DBMS_OUTPUT.PUT_LINE(:new.job_id ||' '|| :new.salary);
check_salary(:new.job_id, :new.salary);
END;

This is my stored procedure:

PROCEDURE check_salary (job_id employees.job_id%TYPE, salary employees.salary%TYPE)
IS
maxSal NUMBER;
minSal NUMBER;
BEGIN
SELECT MAX(salary) INTO maxSal FROM employees WHERE job_id = job_id;
SELECT MIN(salary) INTO minSal FROM employees WHERE job_id = job_id;
IF maxSal >= salary OR minSal <= salary THEN
RAISE_APPLICATION_ERROR(-20001,'Invalid slary '||salary||'. Salaries for job '||job_id||' must be between '||minSal||' and '||maxSal);
ELSE
DBMS_OUTPUT.PUT_LINE('Test');
END IF;
END;

This is how I try to see that the trigger is working:

UPDATE employees SET salary = 100000 WHERE employee_id = 100;

Somehow the DBMS_OUTPUT.PUT_LINE in my Trigger code is working. But the stored procedure causes the error.

question from:https://stackoverflow.com/questions/65601646/call-a-stored-procedure-in-a-trigger-pl-sql

Answer 1

You can't do SELECT or any other DML(INSERT,UPDATE,DELETE) on the table on which trigger is being fired.You have to use compound trigger to get away with mutating table error.

The procedure invoked by trigger is doing a SELECT on the employee table on which trigger is firing and that is forbidden by oracle.

A working example for same issue can be found under, refer UPDATE section Trigger selecting child records, multiplying their values and updating parent record