Dear fahd,
If as your clarification suggests, you are looking for a general
overview of relational databases, a tutorial such as this one from
Oklahoma University is a good place to start.
Dilip's Brief Introduction to Relational Databases:
http://www.cs.unc.edu/Courses/wwwp-s98/members/barman/databaseLesson/index.html
_______________________________________________________________________
How does Data of Database in Database System affect Database Design?
_______________________________________________________________________
Often the database designer would not have much choice in the data
that they receive and have to handle.
The data and more importantly the relationship between the items of
data, determine the “split” of data across the tables. In a sense the
type of data also determines the type of reporting that is likely to
be requested (a later question) and thus influences design through the
idea of planning for efficient data retrieval.
However, the type of data and the expected reporting requirements,
with some commonsense, almost automatically determines the field type
without too many design decisions.
For example the first name data is not going to be stored in a field
of type integer. It is string/text data. However an order code
although primarily numeric may have an alpha prefix and a numeric
field would not be appropriate.
Similarly one would not store “firstname surname” in the one field
because sorting and retrieving is going to be faster if they are
stored in separate fields.
Another example would be that you would separate zip code and state
into their own fields, again for more efficient sorting and retrieval.
The size and nature of the data would also affect which database
product, server, access means may be appropriate.
_______________________________________________________________________
How does Metadata of Database in Database System affect Database
Design?
_______________________________________________________________________
Metadata is data about the data. It may be primarily for the database
designer that includes documentation about the tables, data and data
types etc for the user such as in this example from The Wyoming
Geographic Information Science Center.
www.sdvc.uwyo.edu/metadata/database.html
Thus good sources of metadata can make simplify the tasks of designer,
maintainer and user. It is far simpler and easier to gain an overview
of a complicated database application from Metadata than from
inspecting every field, table, relationship and report.
_______________________________________________________________________
How do Indexes of Database in Database System affect Database Design?
_______________________________________________________________________
The main purpose of indexing is to speed data retrieval. Thus indexes
should be created for the most frequently retrieved fields and or
combinations of fields.
Eg Surname index
______________________________________________________________________
How do Tables of DBMS in Database System affect Database Design?
_______________________________________________________________________
Correct table design is fundamental to a relational database. If the
data is not correctly arranged within the tables, data retrieval and
maintenance can be slower and at worst, almost impossible.
Imagine a sales database with customer details, invoice details within
the one table and product details in another table with no connecting
relationship.
Thus for every sale item, the customer details would be repeated – A
lot of duplication.
Also each product description, price etc would have to be manually
typed into the invoice.
_______________________________________________________________________
How do Forms of DBMS in Database System affect Database Design?
_______________________________________________________________________
Forms are the primary user interface. If there is no postcode field on
a form – the data cannot be collected.
Similarly, if the form specifying the available reports is missing a
report or field, the user cannot generally retrieve the required
report.
Imagine trying to retrieve sales data if there is are no date fields.
_______________________________________________________________________
How do Queries of DBMS in Database System affect Database Design?
_______________________________________________________________________
Queries specify the required data to be retrieved and are often the
underlying intelligence to the report. As mentioned in the answer to
your first question regarding data: queries determine the design of
the database as the data must be present in the database in order to
retrieve it; furthermore a database designer would also keep
efficiency in mind.
For example, you may wish to retrieve sales data on product A by all
salespersonnel and in region B and compare it to region C for sales
dates July through August.
Obviously if you have not previously defined regions in terms of
postcodes or states or countries – the query will be much more
difficult.
_______________________________________________________________________
How do Reports of DBMS in Database System affect Database Design?
_______________________________________________________________________
Because Reporting depends on the underlying queries to the database,
all the previous answers also apply to reporting.
Reporting is the user interface to retrieving the data in the database
and is vitally important to the user’s perception of the database
application. If there “never” seems to be the exact report a user
requires, there view of the entire application may be that it is
useless. The problem arises because often the user is not capable of
generating accurate ad hoc reports, and will depend on the local
Information Systems/Database guru.
Particularly with financial data, it is very easy to generate a query
that should produce the correct data, but doesn’t: “Oh you didn’t want
the order date you wanted the sales date or the posted date or the
warehouse entry date or the average of the 5 dates!”
_______________________________________________________________________
I hope this was these were the kind of answers you were expecting :-)
Please select clarify answer for any specific comments that you would
like explained.
Regards |
