1. Normalization
A337

2. Structure What is a database? Types Tables of information
Rows are referred to as records
Columns are referred to as fields or attributes
Record identifier is referred to as a record key
Types
Relational - Most common, Object-Oriented
Hierarchical, Network (much older types)
A337 - Reed Smith

3. Database structure Two approaches to the structure issue:
Conceptual (you start with the question of “what information should I have?”)
ERD from “scratch”
Empirical (you already know what data there will be - you just want to organize it into tables) –
NORMALIZATION
A337 - Reed Smith

4. Database Tables and Normalization
Normalization - Process for evaluating and correcting table structures to minimize data redundancies
Works through a series of stages called normal forms:
Normal form (1NF)
Second normal form (2NF)
Third normal form (3NF)
There are higher forms but are rarely necessary

5. Normalization Why? How? Data structures need to:
Minimize redundancy
Avoid insertion, update, and deletion anomalies
How?
Restructure information such that:
Only flat (rectangular) files exist (1st normal form) – No Nulls
All items in each record depend upon) the primary record key (2nd normal form) – No Partial Dependencies
If a field depends upon another then the “other” must be a primary key (3rd normal form) – No Transitive Dependencies
A337 - Reed Smith

6. Normalize the following table:
A337 - Reed Smith

7. What is wrong with this solution?
A337 - Reed Smith

8. First Normal Form Eliminate Nulls/Repeating Groups –
Eliminate repeating groups by eliminating nulls, filling in cells with implied values with actual values
Select a primary key
may be a composite key

9. 1NF:
A337 - Reed Smith

10. What is wrong with this solution?
Partial Dependencies
For example, the sales order number is not relevant in the determination of the item name
Similarly, the customer code and customer name do not depend upon the Item ID, they only depend upon the sales order number.
A337 - Reed Smith

11. Second Normal Form Eliminate Partial Dependencies
Write each key component on separate line, and then write the original (composite) key on the last line
Each component will become the key in a new table
Identify the Dependent Attributes
Determine which attributes are dependent on which other attributes

12. Creating 3 Tables
SO_Number, Item_Number
SO_Number,
Item_Number

13. 2NF:
A337 - Reed Smith

14. What is wrong with this solution?
Transitive Dependencies
Notice that the third column of the Sales Orders file has the Customer name and that depends upon the customer number.
But the customer number is not the primary key
A337 - Reed Smith

15. Third Normal Form
For every transitive dependency, write its determinant as a PK for a new table
Identify the attributes dependent on each determinant identified in Step 1 and identify the dependency
Remove the dependent attributes in transitive relationship(s) from each table that has such a transitive relationship
Database Systems: Design, Implementation, & Management, 6th Edition, Rob & Coronel

16. 3NF:
A337 - Reed Smith

17. Denormalization
Creation of normalized relations is important database design goal
Processing requirements should also be a goal
If tables decomposed to conform to normalization requirements
Number of database tables expands

18. Denormalization (continued)
Joining larger number of tables takes additional disk input/output (I/O) operations and processing logic
Reduces system speed
Conflicts among design efficiency, information requirements, and processing speed are often resolved through compromises that may include denormalization
A337
Database Systems: Design, Implementation, & Management, 6th Edition, Rob & Coronel