在插入或更新之前，触发器函数未在 Oracle pl/sql 中执行

Question

INSERT AND UPDATE STATEMENTS IN ANYNIMOUS BLOCK SI NOT CALLING TRIGGER BEACAUSE ERROR IN MY TRIG CODE PLEASE HELP ME TO SOLVE MY MISTAKE AS I AM NOOB IN TRIGGER CONCEPT......

Question: HR Manager wants to keep track of all manager details of every department for auditing in the future. Whenever an HR Manager assigns a new manager, the following manager details should be recorded in DEPT_MANAGER_LOG table.

• department_id : department for which manager is getting assigned or getting modified
• manager_id : employee_id who is being assigned as manager
• start_date : date on which manager is getting assigned for a department
• end_date: end_date of manager (when a manager is assigned the end_date will be null)
• user_name: name of database user who is doing this modification

Whenever an HR Manager changes manager of any department, the end date of previous manager need to be updated and details of new manager need to be inserted in DEPT_MANAGER_LOG table.''' create or replace trigger trg_mgr_log before insert or update of manager_id on departments for each row

CODE:

create or replace trigger trg_mgr_log
before insert or update of manager_id on departments
for each row
declare
v_dpid departments.department_id%type ;
v_mgr_id departments.manager_id%type ;
v_start_date JOB_HISTORY.START_DATE%type;
v_end_date JOB_HISTORY.END_DATE%type;
begin
/*v_dpid := :new.department_id;
select manager_id into v_mgr_id from departments where department_id = v_dpid;*/
select START_DATE, END_DATE into v_start_date, v_end_date from job_history where employee_id = 
v_mgr_id;
if inserting then
v_dpid := :new.department_id;
select manager_id into v_mgr_id from departments where department_id = v_dpid;
if(v_mgr_id is null) then
insert into DEPT_MANAGER_LOG values (v_dpid, :new.manager_id,SYSTIMESTAMP,null,user);
end if;
elsif updating then
v_dpid := :OLD.department_id;
select manager_id into v_mgr_id from departments where department_id = v_dpid;
if(v_mgr_id is not null) then
insert into DEPT_MANAGER_LOG values (v_dpid, :old.manager_id,v_start_date,SYSTIMESTAMP,user);
insert into DEPT_MANAGER_LOG values (v_dpid, :new.manager_id,SYSTIMESTAMP,null,user);
end if;
end if;
end; '

Answer 1

You may be getting a "mutating table" error, because you're selecting from the same table that the trigger is defined on. The following should fix that issue:

create or replace trigger trg_mgr_log
  before insert or update of manager_id on departments
  for each row
begin
  if inserting and
     :new.manager_id is null
  then
    insert into DEPT_MANAGER_LOG values (:new.department_id, :new.manager_id, SYSTIMESTAMP, null, user);
  elsif updating and
        :OLD.manager_id is not null
  then
    declare
      v_start_date JOB_HISTORY.START_DATE%type;
    begin
      select START_DATE
        into v_start_date
        from job_history
        where employee_id = :new.manager_id;
  
      insert into DEPT_MANAGER_LOG values (:OLD.department_id, :old.manager_id, v_start_date, SYSTIMESTAMP, user);
      insert into DEPT_MANAGER_LOG values (:OLD.department_id, :new.manager_id, SYSTIMESTAMP, null,         user);
    end;
  end if;
end;