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

Chapter 3: The Foundation Statements of T-SQL
All duplicate rows were eliminated before the aggregation occurred, so you have substantially fewer rows.
Note that you can use DISTINCT with any aggregate function, although I question whether many of the
functions have any practical use for it. For example, I can’t imagine why you would want an average of
just the DISTINCT rows.
That takes us to the ALL predicate. With one exception, it is a very rare thing indeed to see someone actually
including an ALL in a statement. ALL is perhaps best understood as being the opposite of DISTINCT.
Where DISTINCT is used to filter out duplicate rows, ALL says to include every row. ALL is the default
for any SELECT statement, except for situations where there is a UNION. We will discuss the impact of
ALL in a UNION situation in the next chapter, but for now, realize that ALL is happening any time you
don’t ask for a DISTINCT.
Adding Data with the INSERT Statement
By now you should pretty much have the hang of basic SELECT statements. We would be doing well to
stop here, save for a pretty major problem. We wouldn’t have very much data to look at if we didn’t have
some way of getting it into the database in the first place. That’s where the INSERT statement comes in.
The full syntax for INSERT has several parts:
INSERT [TOP ( ) [PERCENT] ] [INTO]
[()]
[ OUTPUT ]
{ VALUES () [,()] [, …n]
|
| EXEC
| DEFAULT VALUES
This is a bit wordy to worry about now, so let’s simplify it a bit. The more basic syntax for an INSERT
statement looks like this:
INSERT [INTO]
[()]
VALUES () [,()] [, …n]
Let’s look at the parts.
INSERT is the action statement. It tells SQL Server what it is that we’re going to be doing with this statement;
everything that comes after this keyword is merely spelling out the details of that action.
The INTO keyword is pretty much just fluff. Its sole purpose in life is to make the overall statement more
readable. It is completely optional, but I highly recommend its use for the very reason that they added it
to the statement: It makes things much easier to read. As we go through this section, try a few of the
statements both with and without the INTO keyword. It’s a little less typing if you leave it out, but it’s
also quite a bit stranger to read — it’s up to you.
Next comes the table (technically table, view, or a common table expression, but we’re just going to worry
about tables for now) into which you are inserting.
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