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normalizing data

P: 99
does anyone have suggestions on what to read ot get a better understanding of db normalization? i am having issues with my relationships and need a better undertsnaidng. Thanks.
Aug 7 '06 #1
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Expert Mod 10K+
P: 14,534
You only actually need to know 1st, 2nd and 3rd Normal Form.

1st Normal Form
A table is in first normal form if all the key attributes have been defined and it contains no repeating groups.

For example, a customer can place many orders and each order can be for many products.

Therefore, orders are a repeating group for customers and products are a repeating group for orders.

A second table would be created for orders. This table would contain a foreign key reference to the Customer tables unique primary key.

A third table would be created for Products. This table would contain a foreign key reference to the Order tables unique primary key.

2nd Normal Form
A relation is in 2nd Normal Form if it contains no repeating groups as above and every field in the table (excluding foreign keys) is dependent on the Primary key of that table (i.e. there are no partial dependencies).

This is only an issue if the primary key is made up of more than one field. If any field is dependent on only one part of the primary key then the relation is not in 2nd Normal Form.

For example, if your primary key is made up of two foreign keys to the primary keys of two other tables. If any field in the table is only dependent on one of the foreign keys it needs to be removed.

3rd Normal Form
A relation is in 3rd Normal Form when it is in 1st Normal Form, 2nd Normal Form and when 'All non-key attributes are dependent on the key, the whole key and nothing but the key'.

For example, if there are fields in the table which are dependent on a foreign key but not on the primary key they need to be removed.

Hope this helps!!
Aug 8 '06 #2

P: 179
There are some good online tutorials. Under Google, just type "Access Tutorial". Here is one that has 3 entire chapters on relationships, and/or Referential Integrity.

Good Luck.
Aug 8 '06 #3

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