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

Chapter 8: Being Normal: Normalization and Other Basic Design Issues
The First Normal Form
The first normal form (1NF) is all about eliminating repeating groups of data and guaranteeing atomicity
(the data is self-contained and independent). At a high level, it works by creating a primary key (which
we already have), then moving any repeating data groups into new tables, creating new keys for those
tables, and so on. In addition, we break out any columns that combine data into separate rows for each
piece of data.
In the more traditional flat file designs, repeating data was commonplace — as was having multiple
pieces of information in a column. This was rather problematic in a number of ways:
❑ At that time, disk storage was extremely expensive. Storing data multiple times means wasted
space. Data storage has become substantially less expensive, so this isn’t as big an issue as it
once was.
❑ Repetitive data means more data to be moved, and larger I/O counts. This means that performance
is hindered as large blocks of data must be moved through the data bus and or network.
This, even with today’s much faster technology, can have a substantial negative impact on
performance.
❑ The data between rows of what should have been repeating data often did not agree, creating
something of a data paradox and a general lack of data integrity.
❑ If you wanted to query information out of a column that has combined data, then you had to
first come up with a way to parse the data in that column (this was extremely slow).
Now, there are a lot of columns in our table, and I probably could have easily tossed in a few more. Still,
the nice thing about it is that I could query everything out of one place when I wanted to know about
orders.
Just to explore what this means, however, let’s take a look at what some data in this table might look
like. Note that I’m going to cut out a few columns here just to help things fit on a page, but I think you’ll
still be able to see the point:
Order
No
Order
Date
Customer
No
Customer
Name
Customer
Address
100 1/1/99 54545 ACME Co 1234 1st
St.
101 1/1/99 12000 Sneed
Corp.
102 1/1/99 66651 ZZZ &
Co.
555 Main
Ave.
4242 SW
2nd
103 1/2/99 54545 ACME Co 1234 1st
St.
ItemsOrdered
1A4536, Flange, 7lbs, $75;4-OR2400,
Injector, .5lbs, $108;4-OR2403, Injector,
.5lbs, $116;1-4I5436, Head, 63lbs, $750
1-3X9567, Pump, 5lbs, $62.50
7-8G9200; Fan, 3lbs, $84;1-8G5437, Fan,
3lbs, $15;1-3H6250, Control, 5lbs, $32
40-8G9200, Fan, 3lbs, $480;1-2P5523,
Housing, 1lb, $165;1-3X9567, Pump,
5lbs, $42
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