Beginning SQL

Chapter 9
SalesPersonId FirstName LastName Month Year Total
2 Frasier Crane 10 2006 160.83
2 Frasier Crane 10 2006 151.88
2 Frasier Crane 11 2006 12.99
2 Frasier Crane 12 2006 50.90
1 Sandra Hugson 7 2006 12.98
1 Sandra Hugson 8 2006 27.93
1 Sandra Hugson 9 2006 21.93
1 Sandra Hugson 10 2006 44.96
1 Sandra Hugson 11 2006 37.92
1 Sandra Hugson 12 2006 92.89
1 Sandra Hugson 1 2007 31.97
3 Daphne Moon 11 2006 141.85
3 Daphne Moon 12 2006 221.74
Hopefully this example has given you an idea of how to tackle slightly more complex queries. The following
Try It Out puts your knowledge to the test, asking you to write a complex query that identifies
how many repeat customers each salesperson has had.
Try It Out Identifying Repeat Customers
1. Although total sales is a good indicator of a salesperson’s success, the film club chairperson is
interested to know how many people have ordered again from the same salesperson. First, the
chairperson wants to know details of orders where the customer had ordered more than once
from the same salesperson. The SQL to do this is as follows:
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SELECT SalesPerson.SalesPersonId,
SalesPerson.FirstName,
SalesPerson.LastName,
MemberDetails.MemberId,
MemberDetails.FirstName,
MemberDetails.LastName
FROM (Orders INNER JOIN MemberDetails
ON Orders.MemberId = MemberDetails.MemberId)
INNER JOIN SalesPerson
ON Orders.SalesPersonId = SalesPerson.SalesPersonId
GROUP BY SalesPerson.SalesPersonId,
SalesPerson.FirstName,
SalesPerson.LastName,
MemberDetails.MemberId,
MemberDetails.FirstName,
MemberDetails.LastName
HAVING COUNT(Orders.MemberId) > 1
ORDER BY SalesPerson.SalesPersonId;