USE northwind
go
SELECT companyname
FROM customers c
WHERE EXISTS
	(SELECT * FROM orders o
	 WHERE o.customerid = c.customerid
		and orderdate >'1/1/95')
go
SELECT companyname
FROM customers
WHERE customerid IN
	(SELECT customerid	 FROM orders
	 WHERE orderdate >'1/1/95')
go
SELECT distinct companyname
FROM customers c
	JOIN orders o on c.customerid = o.customerid 
 WHERE orderdate >'1/1/95'