Beginning Microsoft SQL Server 2008 ... - S3 Tech Training

Chapter 7: Adding More to Our Queries
There are other possible mixes, but these easily cover the bulk of things that most any SQL developer
will see.
The Output Clause
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The MERGE command also provides us the option of outputting what amounts to a SELECT statement
with the details of what actions were actually performed by the MERGE. The OUTPUT keyword is
essentially a substitute for SELECT, but brings along several special operators to allow us to match up to
the merged data. These include:
❑ $action: Returns INSERTED, UPDATED, or DELETED, as appropriate, to indicate the action taken
for that particular row
❑ inserted: A reference to an internal working table that contains a reference to any data inserted
for a given row, note that this includes the current values for data that has been updated.
❑ deleted: A reference to an internal working table that contains a reference to any data deleted
from a given row, note that this includes the previous values for data that has been updated.
We will visit the inserted and deleted tables in much more detail when we explore triggers in
Chapter 15.
Let’s try these out by resetting our MonthlyRollup table, and executing our MERGE statements again with
the OUTPUT clause included. Start by truncating the MonthlyRollup table to clear out our previous work:
USE AdventureWorks2008
TRUNCATE TABLE Sales.MonthlyRollup;
This clears all data out of our table and resets everything about the table to a state as though it had just
been created using the CREATE command. We’re now ready to execute our first MERGE statement again,
but this time we’ll include the OUTPUT clause:
MERGE Sales.MonthlyRollup AS smr
USING
(
SELECT soh.OrderDate, sod.ProductID, SUM(sod.OrderQty) AS QtySold
FROM Sales.SalesOrderHeader soh
JOIN Sales.SalesOrderDetail sod
ON soh.SalesOrderID = sod.SalesOrderID
WHERE soh.OrderDate >= ‘2003-08-01’ AND soh.OrderDate < ‘2003-08-02’
GROUP BY soh.OrderDate, sod.ProductID
) AS s
ON (s.ProductID = smr.ProductID)
WHEN MATCHED THEN
UPDATE SET smr.QtySold = smr.QtySold + s.QtySold
WHEN NOT MATCHED THEN
INSERT (Year, Month, ProductID, QtySold)
VALUES (DATEPART(yy, s.OrderDate),
DATEPART(m, s.OrderDate),
s.ProductID,
s.QtySold)