This is good! It is a good start on an introduction to databases for
It should be put in the Base manual?
Dan Lewis wrote:
Some basics about creating a database:
1) You begin with data that you want to use for some purpose or purposes.
2) Then you design the database to organize this data so that it will
For example: an address database:
In the beginning, the database consists of information such as
names, addresses, email address, phone numbers, etc.
The first thing you would want to do is to organize this data so
that a name is linked to its address, its email address, its phone
numbers, etc. Now you have rows of data, each one of them containing
information about a single person (a relationship exists between the
data for each row). Each of these pieces of information is a field.
If you look at these rows, you will see that they also contain
some things in common. Several rows can contain data about your
friends, others are about your relatives, and others are about
companies you do business with. You probably know of other
possibilities. So, these rows can be organized into groups based upon
what they have in common. (This too is a relationship.)
The next thing you should do is to further organize these rows in
each one of these groups to make them more useful. You could form a
table using these as the column headings: name, address, email
address, and phone number. ( Now you have a table for each group of
rows. So, if you want data about a particular contact, you can go to
the table that contains it. If you want to look at the data for a
relative, you go to the table containing all of your relatives.
This is basically how a flat database is created. Relational
databases begin in the same way.
At this point, each of these tables are checked to see whether
they are "normal" or not. For example, a contact is likely to have
multiple phone numbers or other possible multiple entries. Each of
these have something in common (another relationship). We can remove
the field containing multiple entries forming a new table. To keep the
relationship between this new table with the original table, we create
a primary-foreign key pair (the primary key is for the new table, and
the foreign key is added to the original table in place of the fields
we removed.) This is what is done to make a table "first normal form".
There are several levels of a table being normal: "first normal
form" to "fourth normal form" and beyond. "Fourth normal form" is
considered to be the standard against which a table should be judged.
The point being that we do not create tables with their fields
and then define the relationship between them. We begin the the fields
that we know we will need, combine the fields based upon relationships
between data, and combine the fields into tables based upon
relationships between the fields. The the tables are normalized up to
"fourth normal form" creating new tables and modifying the old ones.
Primary-foreign key pairs are used to define the relationship of the
new tables and the modified old table from which the new table came.
Hopefully this will help some.
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