Create trigger ORACLE - sql

Question

I have to create a trigger that records order numbers in the purchase table. PURCHASE the training database and audit information into the AUDIT_TAB table. This is a task from the book Christopher Allen How to write powerful and flexible programs on PL / SQL.
CREATE TABLE audit
(ORDER_NUMBER NUMBER(10),
person_code VARCHAR2(3),
user_name CHAR(30),
user_machine CHAR(20),
change_in_quant NUMBER(5),
transaction_time DATE,
FOREIGN KEY (person_code) REFERENCES persoon);
CREATE SEQUENCE order_num_seq;
CREATE OR REPLACE TRIGGER audit_trigger
BEFORE INSERT OR UPDATE ON purchase
FOR EACH ROW
DECLARE
no_name_change EXCEPTION;
quant_change NUMBER(5) := 0;
BEGIN
IF (UPDATING
AND
(:NEW.product_name <> :OLD.product_name))
THEN
RAISE no_name_change;
END IF;
IF (((UPDATING)
AND
(:OLD.ORDER_NUMBER IS NULL))
OR
((INSERTING)
AND
(:NEW.ORDER_NUMBER IS NULL)))
THEN
SELECT order_num_seq.NEXTVAL
INTO :NEW.ORDER_NUMBER
FROM dual;
END IF;
IF (UPDATING)
THEN
quant_change := :NEW. quantity - :OLD. quantity;
ELSE
quant_change := :NEW. quantity;
END IF;
INSERT INTO audit
VALUES ( :NEW.ORDER_NUMBER,
:NEW.salesperson,
USER,
USERENV ( 'TERMINAL' ) ,
quant_change,
SYSDATE) ;
EXCEPTION
WHEN no_name_change
THEN
dbms_output.put_line ('Change of product name not allowed');
dbms_output.put_line ('Aborting and resetting to old values');
:NEW.product_name := :OLD.product_name;
:NEW. salesperson := :OLD.salesperson;
:NEW.ORDER_NUMBER := :OLD.ORDER_NUMBER;
:NEW. quantity := :OLD.quantity;
END audit_trigger ;
/
And trigger compiled with warnings. Why? What's my mistake?
My database:
CREATE TABLE person (
person_code VARCHAR2(3) PRIMARY KEY,
first_name VARCHAR2(15),
last_name VARCHAR2(20),
hire_date DATE
);
CREATE INDEX person_name_index
ON person(last_name, first_name);
ALTER TABLE person
ADD CONSTRAINT person_unique UNIQUE (
first_name,
last_name,
hire_date
);
INSERT INTO person VALUES
('CA', 'Charlene', 'Atlas', '01-ФЕВ-02');
INSERT INTO person VALUES
('GA', 'Gary', 'Andersen', '15-ФЕВ-02' );
INSERT INTO person VALUES
('BB', 'Bobby', 'Barkenhagen', '28-ФЕВ-02');
INSERT INTO person VALUES
('LB', 'Laren', 'Baxter', '01-МАР-02 ');
INSERT INTO person VALUES
('LN', 'Linda', 'Norton', '01-ИЮН-03');
CREATE TABLE product (
product_name VARCHAR2(25) PRIMARY KEY,
product_price NUMBER(4,2),
quantity_on_hand NUMBER(5,0),
last_stock_date DATE
);
ALTER TABLE product ADD (
CONSTRAINT positive_quantity CHECK(
quantity_on_hand IS NOT NULL
AND
quantity_on_hand >= 0)
);
INSERT INTO product VALUES
('Small Widget', 99, 1, '15-ЯНВ-03' );
INSERT INTO product VALUES
( 'Medium Wodget', 75, 1000, '15-ЯНВ-02' );
INSERT INTO product VALUES
('Chrome Phoobar', 50, 100, '15-ЯНВ-03' );
INSERT INTO product VALUES
('Round Chrome Snaphoo', 25, 10000, null);
INSERT INTO product VALUES
('Extra Huge Mega Phoobar +', 9.95, 1234, '15-ЯНВ-04' );
INSERT INTO product VALUES ('Square Zinculator',
45, 1, TO_DATE ('Декабрь 31, 2002, 11:30',
'Month dd, YYYY, HH:MI'));
INSERT INTO product VALUES (
'Anodized Framifier', 49, 5, NULL);
INSERT INTO product VALUES (
'Red Snaphoo', 1.95, 10, '31-ДЕК-01');
INSERT INTO product VALUES (
'Blue Snaphoo', 1.95, 10, '30-ДЕК-01');
CREATE TABLE purchase (
product_name VARCHAR2(25),
salesperson VARCHAR2(3),
purchase_date DATE,
quantity NUMBER(4,2)
);
ALTER TABLE purchase
ADD PRIMARY KEY (product_name,
salesperson,
purchase_date
);
ALTER TABLE purchase ADD (
CONSTRAINT reasonable_date CHECK(
purchase_date IS NOT NULL
AND
TO_CHAR(purchase_date, 'YYYY-MM-DD') >= '2000-06-30')
);
ALTER TABLE purchase
ADD CONSTRAINT purchase_fk_product FOREIGN KEY
(product_name) REFERENCES product;
ALTER TABLE purchase
ADD CONSTRAINT purchase_fk_person FOREIGN KEY
(salesperson) REFERENCES person;
CREATE INDEX purchase_product
ON purchase(product_name);
CREATE INDEX purchase_salesperson
on purchase(salesperson);
INSERT INTO purchase VALUES
('Small Widget', 'CA', '14-ИЮЛ-03', 1);
INSERT INTO purchase VALUES
('Medium Wodget', 'BB', '14-ИЮЛ-03', 75);
INSERT INTO purchase VALUES
('Chrome Phoobar', 'GA', '14-ИЮЛ-03', 2);
INSERT INTO purchase VALUES
('Small Widget', 'GA', '15-ИЮЛ-03', 8);
INSERT INTO purchase VALUES
('Medium Wodget', 'LB', '15-ИЮЛ-03', 20);
INSERT INTO purchase VALUES
('Round Chrome Snaphoo', 'CA', '16-ИЮЛ-03', 5);
INSERT INTO purchase VALUES
('Small Widget', 'CA', '17-ИЮЛ-03', 1);
CREATE TABLE purchase_archive (
product_name VARCHAR2 (25),
salesperson VARCHAR2(3),
purchase_date DATE,
quantity NUMBER (4, 2)
);
INSERT INTO purchase_archive VALUES
('Round Snaphoo', 'BB', '21-ИЮН-01', 10);
INSERT INTO purchase_archive VALUES
('Large Harflinger ' , 'GA', '22-ИЮН-01', 50);
INSERT INTO purchase_archive VALUES
('Medium Wodget', 'LB', '23-ИЮН-01', 20);
INSERT INTO purchase_archive VALUES
('Small Widget', 'ZZ', '24-ИЮН-02', 80);
INSERT INTO purchase_archive VALUES
('Chrome Phoobar', 'CA', '25-ИЮН-02', 2);
INSERT INTO purchase_archive VALUES
('Small Widget', 'JT', '26-ИЮН-02', 50);

Answer 1

There are few errors i can see.
1) Your Purchase table is not having ORDER_NUMBER column which you are trying to use in your code. Add that column and yoour code should work then.
2) Definition of Audit table is not correct. Its referencing a table which doesnot exist. persoon table doesnot exist. Also AUDIT is a reserve keyword, so it should not be used.
You can check those and compile again.
Error you are getting because of spaces between :OLD. quantity . See the working version of code.
CREATE OR REPLACE TRIGGER audit_trigger
BEFORE INSERT OR UPDATE
ON PURCHASE
FOR EACH ROW
DECLARE
no_name_change EXCEPTION;
quant_change NUMBER (5) := 0;
BEGIN
IF (UPDATING AND (:NEW.product_name <> :OLD.product_name))
THEN
RAISE no_name_change;
END IF;
IF ( ( (UPDATING) AND (:OLD.ORDER_NUMBER IS NULL))
OR ( (INSERTING) AND (:NEW.ORDER_NUMBER IS NULL)))
THEN
SELECT order_num_seq.NEXTVAL INTO :NEW.ORDER_NUMBER FROM DUAL;
END IF;
IF (UPDATING)
THEN
quant_change := :NEW.quantity - :OLD.quantity;
ELSE
quant_change := :NEW.quantity;
END IF;
INSERT INTO audit1
VALUES (:NEW.ORDER_NUMBER,
:NEW.salesperson,
USER,
USERENV ('TERMINAL'),
quant_change,
SYSDATE);
EXCEPTION
WHEN no_name_change
THEN
DBMS_OUTPUT.put_line ('Change of product name not allowed');
DBMS_OUTPUT.put_line ('Aborting and resetting to old values');
:NEW.product_name := :OLD.product_name;
:NEW.salesperson := :OLD.salesperson;
:NEW.ORDER_NUMBER := :OLD.ORDER_NUMBER;
:NEW.quantity := :OLD.quantity;
END audit_trigger;
/