Tricky SQl Querry Select Querry

Question

Consider a table

Sales
SAleId Saledate    CustomerID
1  1-may-2012  1
2  1-may-2012  3
3  2-may-2012  1
4  2-may-2012  2
5  3-may-2012  2
i want a querry which will display

customerid saleid   saledate
1  1    1-may-2012
2  4  2-may-2012
3    2  1-may-2012 

Here i want to display list of customers with their first saleid and sale date

Thanks for reply Its Urgent