Oracle SQL. INstructions: Write a PL/SQL function that returns the average retai

Question

Oracle SQL.

INstructions: Write a PL/SQL function that returns the average retail price of all of the books in the books table.

I have this so far but i keep receiving errors:

Create Function GetPrice
RETURN NUMERIC(9, 2) AS
BEGIN

DECLARE @avgRetailPrice AS NUMERIC(9, 2);
SELECT @avgRetailPrice = CAST(AVG(retail) AS NUMERIC(9, 2))

FROM BOOKS;

RETURN @AvgRetailPrice;

END

Attached is the BOOKS table and data:

CREATE TABLE Books
(ISBN VARCHAR2(10),
Title VARCHAR2(30),
PubDate DATE,
PubID NUMBER (2),
Cost NUMBER (5,2),
Retail NUMBER (5,2),
Discount NUMBER (4,2),
Category VARCHAR2(12),
CONSTRAINT books_isbn_pk PRIMARY KEY(isbn),
CONSTRAINT books_pubid_fk FOREIGN KEY (pubid)
REFERENCES publisher (pubid));

INSERT INTO BOOKS
VALUES ('1059831198','BODYBUILD IN 10 MINUTES A DAY','21-JAN-05',4,18.75,30.95, NULL, 'FITNESS');
INSERT INTO BOOKS
VALUES ('0401140733','REVENGE OF MICKEY','14-DEC-05',1,14.20,22.00, NULL, 'FAMILY LIFE');
INSERT INTO BOOKS
VALUES ('4981341710','BUILDING A CAR WITH TOOTHPICKS','18-MAR-06',2,37.80,59.95, 3.00, 'CHILDREN');
INSERT INTO BOOKS
VALUES ('8843172113','DATABASE IMPLEMENTATION','04-JUN-03',3,31.40,55.95, NULL, 'COMPUTER');
INSERT INTO BOOKS
VALUES ('3437212490','COOKING WITH MUSHROOMS','28-FEB-04',4,12.50,19.95, NULL, 'COOKING');
INSERT INTO BOOKS
VALUES ('3957136468','HOLY GRAIL OF ORACLE','31-DEC-05',3,47.25,75.95, 3.80, 'COMPUTER');
INSERT INTO BOOKS
VALUES ('1915762492','HANDCRANKED COMPUTERS','21-JAN-05',3,21.80,25.00, NULL, 'COMPUTER');
INSERT INTO BOOKS
VALUES ('9959789321','E-BUSINESS THE EASY WAY','01-MAR-06',2,37.90,54.50, NULL, 'COMPUTER');
INSERT INTO BOOKS
VALUES ('2491748320','PAINLESS CHILD-REARING','17-JUL-04',5,48.00,89.95, 4.50, 'FAMILY LIFE');
INSERT INTO BOOKS
VALUES ('0299282519','THE WOK WAY TO COOK','11-SEP-04',4,19.00,28.75, NULL, 'COOKING');
INSERT INTO BOOKS
VALUES ('8117949391','BIG BEAR AND LITTLE DOVE','08-NOV-05',5,5.32,8.95, NULL, 'CHILDREN');
INSERT INTO BOOKS
VALUES ('0132149871','HOW TO GET FASTER PIZZA','11-NOV-06',4,17.85,29.95, 1.50, 'SELF HELP');
INSERT INTO BOOKS
VALUES ('9247381001','HOW TO MANAGE THE MANAGER','09-MAY-03',1,15.40,31.95, NULL, 'BUSINESS');
INSERT INTO BOOKS
VALUES ('2147428890','SHORTEST POEMS','01-MAY-05',5,21.85,39.95, NULL, 'LITERATURE');

Explanation / Answer

Create Function GetPrice RETURN NUMERIC(9, 2) AS

avgRetailPrice NUMERIC(9, 2);

BEGIN

SELECT AVG(retail) into avgRetailPrice FROM BOOKS group by BOOKS.ISBN;

RETURN avgRetailPrice;

END

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