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

Chapter 7: Adding More to Our Queries
Which is quite a bit different from what CAST did. Indeed, you could have converted to any one of 34
two-digit- or four-digit-year formats.
SELECT OrderDate, CONVERT(varchar(12), OrderDate, 5) AS Converted
FROM Sales.SalesOrderHeader
WHERE SalesOrderID = 43663;
This returns:
OrderDate Converted
----------------------- ------------
2001-07-01 00:00:00.000 01-07-01
(1 row(s) affected)
All you need is to supply a code at the end of the CONVERT function (111 in the preceding example gave
us the Japan standard, with a four-digit year, and 5 the Italian standard, with a two-digit year) that tells
which format you want. Anything in the 100s is a four-digit year; anything less than 100, with a few
exceptions, is a two-digit year. The available formats can be found in Books Online under the topic of
CONVERT or CASE.
Keep in mind that you can set a split point that SQL Server will use to determine whether a two-digit
year should have a 20 added on the front or a 19. The default breaking point is 49/50 — a two-digit year
of 49 or less will be converted using a 20 on the front. Anything higher will use a 19. These can be changed
in the database server configuration (administrative issues are discussed in Chapter 19).
The MERGE Command
206
The MERGE command is new with SQL Server 2008 and provides a somewhat different way of thinking
about DML statements. With MERGE, we have the prospect of combining multiple DML action statements
(INSERT, UPDATE, DELETE) into one overall action, improving performance (they can share many of the
same physical operations) and simplifying transactions. MERGE makes use of a special USING clause that
winds up working somewhat like a CTE. The result set in the USING clause can then be used to conditionally
apply your INSERT, UPDATE, and DELETE statements. The basic syntax looks something like this:
MERGE [ TOP ( ) [ PERCENT ] ]
[ INTO ] [ WITH ( ) ] [ [ AS ] ]
USING
ON
[ WHEN MATCHED [ AND ]
THEN ]
[ WHEN NOT MATCHED [ BY TARGET ] [ AND ]
THEN ]
[ WHEN NOT MATCHED BY SOURCE [ AND ]
THEN ]
[ ]
[ OPTION ( [ ,...n ] ) ];
Let’s use the example of receiving a shipment for inventory. We’ll assume that we’re keeping a special
roll up table of our sales for reporting purposes. We want to run a daily query that will add any new
sales to our monthly rollup. On the first night of the month, this is pretty much a no-brainer, as, since