How to solve this using a subquery in a from clause? - sql

Question

Display author, title, retail and retail price of all books whose retail price is the highest for the specific author.
I have the query below. I'm kinda confused how to do a subquery in a from clause.
select lname, fname, title, retail
from author natural join bookauthor
natural join books
where retail=(select max(retail)
from books);
Below is the data from the database that I'm using
FNAME LNAME TITLE RETAIL
---------- ---------- ------------------------------ ----------
SAM SMITH BODYBUILD IN 10 MINUTES A DAY 30.95
LISA PORTER BODYBUILD IN 10 MINUTES A DAY 30.95
JANICE JONES REVENGE OF MICKEY 22
TAMARA KZOCHSKY BUILDING A CAR WITH TOOTHPICKS 59.95
TINA PETERSON DATABASE IMPLEMENTATION 55.95
JUAN ADAMS DATABASE IMPLEMENTATION 55.95
JAMES AUSTIN DATABASE IMPLEMENTATION 55.95
JACK BAKER COOKING WITH MUSHROOMS 19.95
JAMES AUSTIN HOLY GRAIL OF ORACLE 75.95
LISA WHITE HANDCRANKED COMPUTERS 25
WILLIAM WHITE HANDCRANKED COMPUTERS 25
JANICE JONES E-BUSINESS THE EASY WAY 54.5
ROBERT ROBINSON PAINLESS CHILD-REARING 89.95
OSCAR FIELDS PAINLESS CHILD-REARING 89.95
JACK BAKER PAINLESS CHILD-REARING 89.95
SAM SMITH THE WOK WAY TO COOK 28.75
ROBERT ROBINSON BIG BEAR AND LITTLE DOVE 8.95
SAM SMITH HOW TO GET FASTER PIZZA 29.95
WILLIAM WHITE HOW TO MANAGE THE MANAGER 31.95
LISA WHITE SHORTEST POEMS 39.95
20 rows selected.

Answer 1

You could use this:
SELECT lname, fname, title, retail
FROM author a
INNER JOIN bookauthor ba
ON a.id = ba.author_id
INNER JOIN books b
ON b.id = ba.book_id
WHERE (ba.author_id, ba.retail) IN (
SELECT ba1.author_id, MAX(b1.retail)
FROM books b1
INNER JOIN bookauthor ba1
ON ON b1.id = ba1.book_id
GROUP BY ba1.author_id
);
Do not use NATURE JOIN. This is bad way of join, for all learner and programmer.
(And change author_id, book_id to column name of your specific table)
Other way:
SELECT lname, fname, title, retail
FROM author a
INNER JOIN bookauthor ba
ON a.id = ba.author_id
INNER JOIN books b
ON b.id = ba.book_id
INNER JOIN(
SELECT ba1.author_id, MAX(b1.retail) retail
FROM books b1
INNER JOIN bookauthor ba1
ON ON b1.id = ba1.book_id
GROUP BY ba1.author_id
) mr
ON
ba.author_id = mr.author_id
AND ba.retail = mr.retail
;

Answer 2

This can be solved using ether an inner join:
select lname, fname, title, retail
from author natural join bookauthor
natural join books
inner join (select max(retail) as max_retail, authorid
from books
group by authorid) b
on books.authorid = b.authorid and books.retail = b.max_retail
or a correlated subquery:
select lname, fname, title, retail
from author natural join bookauthor
natural join books
where retail=(select max(retail)
from books b where b.authorid=author.authorid);
Please note, because you are using the natural join it is impossible for us to know the actual column names you used for the joins. Therefore I have assumed that the authorid foreign key is called authorid