Normalization
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The document discusses database normalization. It begins with a brief history of normalization, introduced by Edgar Codd in 1970. It then defines database normalization as removing redundant data to improve storage efficiency, data integrity, and scalability. The document provides examples to illustrate the concepts of first, second, and third normal forms. It shows how a book database can be normalized by separating data into separate tables for authors, subjects, and books and defining relationships between the tables using primary and foreign keys. This normalization process addresses issues like redundant data, data integrity, and scalability.
Normalization
- 1. NORMALIZATION BY, SALMAN_MEMON 2K12/IT/109
- 2. HISTORY Edgar F. Codd, the inventor of the relational model, introduced the concept of normalization and what we now know as the first normal form (1NF) in 1970. Codd went on to define the second normal form (2nf) and third normal form (3nf) in 1971
- 3. DATABASE NORMALIZATION • Database normalization is the process of removing redundant data from your tables in to improve storage efficiency, data integrity, and scalability. • In the relational model, methods exist for quantifying how efficient a database is. These classifications are called normal forms (or NF), and there are algorithms for converting a given database between them. • Normalization generally involves splitting existing tables into multiple ones, which must be re-joined or linked each time a query is issued.
- 4. NORMAL FORM Edgar F. Codd originally established three normal forms: 1NF, 2NF and 3NF. There are now others that are generally accepted, but 3NF is widely considered to be sufficient for most applications. Most tables when reaching 3NF are also in BCNF (boyce-codd normal form).
- 5. TABLE 1 Title Author1 Author 2 ISBN Subject Pages Publisher Database System Concepts Abraham Silberschatz Henry F. Korth 0072958863 MySQL, Computer s 1168 McGraw- Hill Operating System Concepts Abraham Silberschatz Henry F. Korth 0471694665 Computer s 944 McGraw- Hill
- 6. TABLE 1 PROBLEMS • This table is not very efficient with storage. • This design does not protect data integrity. • Third, this table does not scale well.
- 7. FIRST NORMAL FORM • In our table 1, we have two violations of first normal form: • First, we have more than one author field, • Second, our subject field contains more than one piece of information. With more than one value in a single field, it would be very difficult to search for all books on a given subject.
- 8. FIRST NORMAL TABLE • TABLE 2 Title Author ISBN Subject Pages Publisher Database System Concepts Abraham Silberschatz 0072958863 MySQL 1168 McGraw-Hill Database System Concepts Henry F. Korth 0072958863 Computers 1168 McGraw-Hill Operating System Concepts Henry F. Korth 0471694665 Computers 944 McGraw-Hill Operating System Concepts Abraham Silberschatz 0471694665 Computers 944 McGraw-Hill
- 9. • We now have two rows for a single book. Additionally, we would be violating the second normal form… • A better solution to our problem would be to separate the data into separate tables- an author table and a subject table to store our information, removing that information from the book table:
- 10. Subject_ID Subject 1 MySQL 2 Computers Author_ID Last Name First Name 1 Silberschat z Abraham 2 Korth Henry ISBN Title Pages Publisher 0072958863 Database System Concepts 1168 McGraw-Hill 0471694665 Operating System Concepts 944 McGraw-Hill Subject Table Author Table Book Table
- 11. • Each table has a primary key, used for joining tables together when querying the data. A primary key value must be unique with in the table (no two books can have the same ISBN number), and a primary key is also an index, which speeds up data retrieval based on the primary key. • Now to define relationships between the tables
- 12. RELATIONSHIPS ISBN Author_ID 0072958863 1 0072958863 2 0471694665 1 0471694665 2 ISBN Subject_ID 0072958863 1 0072958863 2 0471694665 2 Book_Author Table Book_Subject Table
- 13. SECOND NORMAL FORM • As the first normal form deals with redundancy of data across a horizontal row, second normal form (or 2NF) deals with redundancy of data in vertical columns. • As stated earlier, the normal forms are progressive, so to achieve second normal form, the tables must already be in first normal form. • The book table will be used for the 2nf example
- 14. 2NF TABLE Publisher_ID Publisher Name 1 McGraw-Hill ISBN Title Pages Publisher_ID 0072958863 Database System Concepts 1168 1 0471694665 Operating System Concepts 944 1 Publisher Table Book Table
- 15. 2NF • Here we have a one-to-many relationship between the book table and the publisher. A book has only one publisher, and a publisher will publish many books. When we have a one-to-many relationship, we place a foreign key in the book table, pointing to the primary key of the publisher table. • The other requirement for second normal form is that you cannot have any data in a table with a composite key that does not relate to all portions of the composite key.
- 16. THIRD NORMAL FORM • Third normal form (3NF) requires that there are no functional dependencies of non-key attributes on something other than a candidate key. • A table is in 3nf if all of the non-primary key attributes are mutually independent • There should not be transitive dependencies