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

Now let’s try taking a little bit more specific information. Let’s say all we want is a list of all our customers
by last name:
SELECT LastName FROM Person.Person;
Your results should look something like:
Achong
Abel
Abercrombie
...
He
Zheng
Hu
Note that I’ve snipped rows out of the middle for brevity. You should have 19,972 rows. Since the last
name of each customer is all that we want, that’s all that we’ve selected.
Many SQL writers have the habit of cutting their queries short and always selecting every column by
using a * in their selection criteria. This is another one of those habits to resist. While typing in a * saves
you a few moments of typing out the column names that you want, it also means that more data has to
be retrieved than is really necessary. In addition, SQL Server must figure out just how many columns
“*” amounts to and what specifically they are. You would be surprised at just how much this can drag
down your application’s performance and that of your network. In short, a good rule to live by is to
select what you need — that is, exactly what you need. No more, no less.
Let’s try another simple query. How about:
SELECT Name FROM Production.Product;
Again, assuming that you haven’t modified the data that came with the sample database, SQL Server should
respond by returning a list of 504 different products that are available in the AdventureWorks database:
Name
----------------------------------------
Adjustable Race
Bearing Ball
BB Ball Bearing
...
...
Road-750 Black, 44
Road-750 Black, 48
Road-750 Black, 52
Chapter 3: The Foundation Statements of T-SQL
The columns that you have chosen right after your SELECT clause are known as the SELECT list. In short,
the SELECT list is made up of the columns that you have requested be output from your query.
The columns that you have chosen right after your SELECT clause are known as the
SELECT list.
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