Join vs. sub-query

Question

I am an old-school MySQL user and have always preferred JOIN over sub-query. But nowadays everyone uses sub-query, and I hate it; I don\'t know why.

Answer 1

Subqueries have ability to calculate aggregation functions on a fly. E.g. Find minimal price of the book and get all books which are sold with this price. 1) Using Subqueries:

SELECT titles, price
FROM Books, Orders
WHERE price = 
(SELECT MIN(price)
 FROM Orders) AND (Books.ID=Orders.ID);

2) using JOINs

SELECT MIN(price)
     FROM Orders;
-----------------
2.99

SELECT titles, price
FROM Books b
INNER JOIN  Orders o
ON b.ID = o.ID
WHERE o.price = 2.99;