A Gentle Introduction to

SQL

Graduated questions

ER diagram for the Southwind database:

Entity relation diagram er3

0a	The table tpurcdgives details of all products ordered. This table gives details of all purchase orders.	SELECT * FROM tcust, tpurcd, tprod WHERE tcust.code=tpurcd.cust AND tpurcd.prod=tprod.code

0b	Some of the tables are joined by a composite foreign key. For example to link shipment details to a shipment record we must join on (cust,shpd).	SELECT addr, tship.shpd, prod FROM tship, tshipd WHERE tshipd.cust=tship.cust AND tshipd.shpd=tship.shpd AND tship.addr IS NOT NULL