Insertion using triggers by passing values - plsql

Question

Lets say I have a table as follows--
create table employees
(
eno number(4) not null primary key,
ename varchar2(30),
zip number(5) references zipcodes,
hdate date
);
And I'm trying to create a trigger with--
CREATE OR REPLACE TRIGGER TWELVE_ONE
BEFORE INSERT OR UPDATE
ON EMPLOYEES
FOR EACH ROW
DECLARE
V_DATE VARCHAR2 (10);
BEGIN
SELECT TO_CHAR (SYSDATE, 'hh24:mi:ss') INTO V_DATE FROM DUAL;
IF (V_DATE >= '12:00:01' AND V_DATE < '13:00:00')
THEN
INSERT INTO TABLE ?????
ELSE
ROLLBACK? TERMINATE TRANSACTION?
END IF;
END;
Purpose of the trigger is to allow an insertion/update during 12:00-13:00 and prevent the insertion at any other time. The trigger construction (thanks to #Melkikun) is seems ok. However now I'm facing the following issues--
How is it possible to pass the values here? I mean lets say my create statement is:
Insert into employees Values (1, 'someone', 11111, '17-12-2015')
And lets say the time is 12:30:01 now. How would the trigger perform the insertion without knowing the values?
And lets say the time is now 13:00:1 now. How would the trigger stop/prevent the insertion?
I'm using Oracle SQL Developer 4.02.15
Many Thanks

Answer 1

You just have to do it the other way.
If the time is not correct,then you raise an exception, so the insert won't be done.
CREATE OR REPLACE TRIGGER TWELVE_ONE
BEFORE INSERT OR UPDATE
ON EMPLOYEES
FOR EACH ROW
DECLARE
V_DATE VARCHAR2 (10);
MyException exception;
BEGIN
SELECT TO_CHAR (SYSDATE, 'hh24:mi:ss') INTO V_DATE FROM DUAL;
IF (V_DATE < '12:00:01' OR V_DATE > '13:00:00')
THEN
raise MyException;
END IF;
EXCEPTION
When MyException then
ROLLBACK;
//output message ...
END;
How would the trigger perform the insertion without knowing the values?
The trigger knows the value thanks to :NEW and :OLD.
You normally use the terms in a trigger using :old to reference the old value and :new to reference the new value.So you will have :NEW.eno ,:NEW.ename ...
Here is an example from the Oracle documentation :
CREATE OR REPLACE TRIGGER Print_salary_changes
BEFORE DELETE OR INSERT OR UPDATE ON Emp_tab
FOR EACH ROW
WHEN (new.Empno > 0)
DECLARE
sal_diff number;
BEGIN
sal_diff := :new.sal - :old.sal;
dbms_output.put('Old salary: ' || :old.sal);
dbms_output.put(' New salary: ' || :new.sal);
dbms_output.put_line(' Difference ' || sal_diff);
END;