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

❑ Date of hire
❑ Date terminated (if there is one)
❑ The employee’s manager
❑ Department
Start by trying to figure out a layout for yourself.
Before we start looking at this together, let me tell you not to worry too much if your layout isn’t exactly
like mine. There are as many database designs as there are database designers — and that all begins with
table design. We all can have different solutions to the same problem. What you want to look for is
whether you have all the concepts that need to be addressed. That being said, let’s take a look at one
way to build this table.
We have a special column here. The EmployeeID is to be generated by the system and therefore is an
excellent candidate for either an identity column or a ROWGUIDCOL. There are several reasons you might
want to go one way or the other between these two, but we’ll go with an identity column for a couple of
reasons:
❑ It’s going to be used by an average person. (Would you want to have to remember a GUID?)
❑ It incurs lower overhead.
We’re now ready to start constructing our script:
CREATE TABLE Employees
(
EmployeeID int IDENTITY NOT NULL,
Chapter 5: Creating and Altering Tables
For this column, the NOT NULL option has essentially been chosen for us by virtue of our use of an
IDENTITY column. You cannot allow NULL values in an IDENTITY column. Note that, depending on our
server settings, we will, most likely, still need to include our NOT NULL option (if we leave it to the
default we may get an error depending on whether the default allows NULLs).
Next up, we want to add in our name columns. I usually allow approximately 25 characters for names.
Most names are far shorter than that, but I’ve bumped into enough that were rather lengthy (especially
since hyphenated names have become so popular) that I allow for the extra room. In addition, I make
use of a variable-length data type for two reasons:
❑ To recapture the space of a column that is defined somewhat longer than the actual data usually
is (retrieve blank space)
❑ To simplify searches in the WHERE clause — fixed-length columns are padded with spaces,
which requires extra planning when performing comparisons against fields of this type
The exception in this case is the middle initial. Since we really need to allow for only one character here,
recapture of space is not an issue. Indeed, a variable-length data type would actually use more space in
this case, since a varchar needs not only the space to store the data, but also a small amount of overhead
space to keep track of how long the data is. In addition, ease of search is not an issue since, if we
have any value in the field at all, there isn’t enough room left for padded spaces.
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