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

efore, but remove the two AS keywords from the query — you’ll see that you wind up with exactly the
same results. It’s also worth noting that you can alias any column (and even, as we’ll see in the next
chapter, table names), not just aggregates.
Let’s re-run this last query, but this time we’ll not use the AS keyword in some places, and we’ll alias
every column:
SELECT SalesOrderID AS “Order Number”, MIN(OrderQty) MinOrderQty, MAX(OrderQty)
MaxOrderQty
FROM Sales.SalesOrderDetail
WHERE SalesOrderID IN (43660, 43670, 43672)
GROUP BY SalesOrderID;
Despite the AS keyword being missing in some places, we’ve still changed the name output for every
column:
Order Number MinOrderQty MaxOrderQty
------------ ----------- -----------
43660 1 1
43670 1 2
43672 1 6
(3 row(s) affected)
I must admit that I usually don’t include the AS keyword in my aliasing, but I would also admit that
it’s a bad habit on my part. I’ve been working with SQL Server since before the AS keyword was available
and have, unfortunately, become set in my ways about it (I simply forget to use it). I would, however,
strongly encourage you to go ahead and make use of this extra word. Why? Well, first because it
reads somewhat more clearly, and second, because it’s the ANSI/ISO standard way of doing things.
So then, why did I even tell you about it? Well, I got you started doing it the right way — with the AS
keyword — but I want you to be aware of alternate ways of doing things, so that you aren’t confused
when you see something that looks a little different.
COUNT(Expression|*)
The COUNT(*) function is about counting the rows in a query. To begin with, let’s go with one of the
most common varieties of queries:
SELECT COUNT(*)
FROM HumanResources.Employee
WHERE HumanResources.Employee.BusinessEntityID = 5;
The record set you get back looks a little different from what you’re used to from earlier queries:
-----------
1
(1 row(s) affected)
Chapter 3: The Foundation Statements of T-SQL
59