SELECT*FROM customers C, orders O, orderitems OI WHERE C.cust_id = O.cust_id AND OI.order_num = O.order_num AND prod_id ='RGAN01';
Self-association
SELECT*FROM customers c1, customers c2 WHERE c1.cust_name = c2.cust_name AND c2.cust_contact ='Jim Jones';
Natural connection
SELECT c.*, o.order_num, o.order_date FROM customers c, orders o, orderitems oi WHERE c.cust_id = o.cust_id AND oi.order_num = o.order_num AND prod_id ='RGAN01';
External connection
SELECT*FROM customers LEFTOUTERJOIN orders ON customers.cust_id = orders.cust_id;
SELECT*FROM customers RIGHTOUTERJOIN orders ON customers.cust_id = orders.cust_id;
Use joins with aggregate functions
SELECT customers.cust_id,COUNT(orders.order_num)AS num_ord FROM customers INNERJOIN orders ON customers.cust_id = orders.cust_id GROUPBY customers.cust_id;
SELECT customers.cust_id,COUNT(orders.order_num)AS num_ord FROM customers LEFTJOIN orders ON customers.cust_id = orders.cust_id GROUPBY customers.cust_id;