Beginning SQL

Advanced Queries
What you really want, however, is to group the orders according to the month and year in which they
were placed, necessitating a GROUP BY clause:
SELECT FirstName, LastName,MONTH(OrderDate)AS Month, YEAR(OrderDate) As Year
FROM Orders INNER JOIN SalesPerson
ON Orders.SalesPersonId = SalesPerson.SalesPersonId
GROUP BY FirstName,LastName,MONTH(OrderDate), YEAR(OrderDate);
Executing the preceding query groups the results by salesperson, month, and year, as shown in the following
table:
FirstName LastName Month Year
Daphne Moon 1 2007
Daphne Moon 11 2006
Daphne Moon 12 2006
Frasier Crane 10 2006
Frasier Crane 11 2006
Frasier Crane 12 2006
Sandra Hugson 1 2007
Sandra Hugson 7 2006
Sandra Hugson 8 2006
Sandra Hugson 9 2006
Sandra Hugson 10 2006
Sandra Hugson 11 2006
Sandra Hugson 12 2006
So far, you have a list of salespeople as well as month and year values. There’s no link to the items contained
in each order. Your next task is to link the current tables, SalesPerson and Orders, to items in each
order. This data is contained in the OrderItems table, which is the next table to which you must create a
link. The value that links the current tables and OrderItems is the OrderId present in the Orders and
OrderItems tables. Join OrderItems to the current tables using an inner join, as illustrated in the following
statement:
SELECT FirstName, LastName,MONTH(OrderDate)AS Month, YEAR(OrderDate) AS Year
FROM (Orders INNER JOIN SalesPerson ON Orders.SalesPersonId =
SalesPerson.SalesPersonId)
INNER JOIN OrderItems ON OrderItems.OrderId = Orders.OrderId
GROUP BY FirstName,LastName,MONTH(OrderDate), YEAR(OrderDate);
If you run this query, you won’t see any difference between these results and the previous results. Also,
what you’re really after is the total cost of all orders placed in each month by each salesperson, which is
represented by the SUM(DVDPrice) data in the original SELECT list described previously. However, the
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