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

Chapter 3: The Foundation Statements of T-SQL
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Let’s look at the differences. First, as with all columns that are returned as a result of a function call,
there is no default column name. If you want there to be a column name, then you need to supply an
alias. Next, you’ll notice that we haven’t really returned much of anything. So what does this record set
represent? It is the number of rows that matched the WHERE condition in the query for the table(s) in the
FROM clause.
Keep this query in mind. This is a basic query that you can use to verify that the exact
number of rows that you expect to be in a table and match your WHERE condition are
indeed in there.
Just for fun, try running the query without the WHERE clause:
SELECT COUNT(*)
FROM HumanResources.Employee;
If you haven’t done any deletions or insertions into the Employee table, then you should get a record set
that looks something like this:
-----------
290
(1 row(s) affected)
What is that number? It’s the total number of rows in the Employee table. This is another one to keep in
mind for future use.
Now, we’re just getting started! If you look back at the header for this section (the COUNT section), you’ll
see that there are two different ways of using COUNT. We’ve already discussed using COUNT with the *
option. Now it’s time to look at it with an expression — usually a column name.
First, try running the COUNT the old way, but against a new table:
SELECT COUNT(*)
FROM Person.Person;
This is a slightly larger table, so you get a higher COUNT:
-----------
19972
(1 row(s) affected)
Now alter your query to select the count for a specific column:
SELECT COUNT(AdditionalContactInfo)
FROM Person.Person;