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

Chapter 3: The Foundation Statements of T-SQL
While T-SQL is unique to SQL Server, the statements you use most of the time are not. T-SQL is largely
ANSI/ISO compliant (The standard was originally governed by ANSI, and was later taken over by the
ISO. It was ANSI long enough that people generally still refer to it as ANSI compliance.), which means
that, by and large, it complies with a very wide open standard. What this means to you as a developer is that
much of the SQL you’re going to learn in this book is directly transferable to other SQL-based database
servers such as Sybase (which long ago used to share the same code base as SQL Server), Oracle, DB2,
and MySQL. Be aware, however, that every RDBMS has different extensions and performance enhancements
that it uses above and beyond the ANSI/ISO standard. I will try to point out the ANSI vs. non-
ANSI ways of doing things where applicable. In some cases, you’ll have a choice to make — performance
versus portability to other RDBMS systems. Most of the time, however, the ANSI way is as fast as any
other option. In such a case, the choice should be clear: Stay ANSI compliant.
Getting Star ted with a Basic SELECT
Statement
If you haven’t used SQL before, or don’t feel like you’ve really understood it yet, pay attention here! The
SELECT statement and the structures used within it form the basis of the lion’s share of all the commands
we will perform with SQL Server. Let’s look at the basic syntax rules for a SELECT statement:
SELECT [ALL|DISTINCT] [TOP () [PERCENT] [WITH TIES]]
[FROM ]
[WHERE ]
[GROUP BY ]
[HAVING ]
[ORDER BY ]
[[FOR XML {RAW|AUTO|EXPLICIT|PATH [()]}[, XMLDATA][, ELEMENTS][, BINARY
base 64]]
[OPTION (, [, ...n])]
Wow — that’s a lot to decipher, so let’s look at the parts.
Note that the parentheses around the TOP expression are, technically speaking, optional. Microsoft
refers to them as “required,” then points out that a lack of parentheses is actually supported, but for
backward compatibility only. This means that Microsoft may pull support for that in a later release, so if
you do not need to support older versions of SQL Server, I strongly recommend using parentheses to
delimit a TOP expression in your queries.
The SELECT Statement and FROM Clause
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The verb — in this case a SELECT — is the part of the overall statement that tells SQL Server what we are
doing. A SELECT indicates that we are merely reading information, as opposed to modifying it. What we
are selecting is identified by an expression or column list immediately following the SELECT. You’ll see
what I mean by this in a moment.
Next, we add in more specifics, such as where we are getting this data. The FROM statement specifies the
name of the table or tables from which we are getting our data. With these, we have enough to create a