Normalization.riz
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The document discusses database normalization through three normal forms (1NF, 2NF, 3NF). 1NF structures data into tables, removes repeating groups, and requires a primary key. 2NF removes redundant data across rows. 3NF removes transitive dependencies, where a non-key field depends on another non-prime attribute. The document provides examples of denormalizing and normalizing sample data through these three forms.
Normalization.riz
- 1. Normalization 1st ,2nd and 3rd Normal Form By Rizwan , A.Rehman And Imran
- 2. Normalization(def) • The Process of producing a simple and more reliable database structure. Or • Normalization is a process of moving data into related field. • This process works through different stages known as normal form. • These stages are 1st ,2nd ,and 3rd normal form.
- 3. Purpose of Normalization • It makes the database design efficient in performance. • It reduce the amount of data if possible. • It makes the database design free of update , insertion and deletion problems. • It identifies relationship between entities.
- 4. Characteristics of normalized Database • Each relation must have a key field. • All fields must contain atomic data. • There must be no repeating fields. • Each table must contain information about a single entity. • Each field in a relation must depend on key field. • All non-key fields must be mutually independent.
- 5. Users Users requirement Specification Source like Data dictionary & Data Model Data Source Second Normal Form(2NF) First Normalized Form(1NF) Un-Normal Form(UNF) Third Normal Form(3NF) Transfer attributed into Table format Remove repeating groups Remove Partial dependencies Remove transitive dependencies
- 6. 1st Normal Form The Requirements • Each table has a primary key: minimal set of attributes which can uniquely identify a record. • The values in each column of a table are atomic (No multi-value attributes allowed). • There are no repeating groups: two columns do not store similar information in the same table.
- 7. 1st NF Example Accountant # Skill # Skill Category Proficiency # Accountant Name Accountant Age Group # Grou p Super visor 21 113 Systems 3 Ali 55 52 Baber 35 113 179 204 Systems Tax Audit 5 1 6 Daud 32 44 Ali 50 179 Tax 2 Chohan 40 44 Ali 77 148 179 Consulting Tax 6 6 Zahid 52 52 Baber The above relation is un-normalize because it contain repeating groups of three attributes Skill number, Skill category and Proficiency number.
- 8. 1st NF Example Accountant # Skill # Skill Category Proficienc y # Accountant Name Accountant Age Group # Group Supervi sor 21 113 Systems 3 Ali 55 52 Baber 35 113 Systems 5 Daud 32 44 Ali 35 179 Tax 1 Daud 32 44 Ali 35 204 Audit 6 Daud 32 44 Ali 50 179 Tax 2 Chohan 40 44 Ali 77 148 Consulting 6 Zahid 52 52 Baber 77 179 Tax 6 Zahid 52 52 Baber Normalize Form Primary Key
- 9. Problems Of 1NF Updating Problem: Suppose user want to change name Accountant # 35 to M.Daud. He has to name all record in which accountant number 35 appears. Inconsistent Data: The above table may contain inconsistent data. There are three records of Accountant # 35.It is possible that there are two different names with Account number 35 in two different records. The user can make this error during updating. Addition Problem: Suppose the user want to add another skill number in the table. It is not possible until an Accountant with that skill exists because both skill number and Accountant Number are used as primary key. Deletion Problem: Suppose the user want to delete the record of Supervisor Ali.If he delete the whole record in which Ali appears, the information about Accountant will also be lost.
- 10. 2nd Normal Form The Requirements • All requirements for 1st NF must be met. • Redundant data across multiple rows of a table must be moved to a separate table. • The above relation in 1NF has some attributes which are not depending on the primary key. E.g. Accountant Name, Accountant Age, And group Information is determined by Accountant Number and is not dependent on skill. The following relation can be created in which all attributes are fully dependent on primary key account number.
- 11. Accountant # Accountant Name Accountant Age Group # Group Supervisor 21 Ali 55 52 Baber 35 Daud 32 44 Ali 50 Chohan 40 44 Ali 70 Zahid 52 52 Baber Primary Key Skill Number Skill Category 113 System 179 Tax 204 Audit 148 Consulting Similarly , Another relation skill can be created in which all fields are fully dependent on the primary key as follows. Primary Key The attribute Proficiency in 1NF relation was fully dependent on the whole primary key. The proficiency require to know the accountant number and skill number. The third relation will be create as follows. Skill Table in 2NF Accountant Table in 2NF
- 12. Accountant Number Skill Number Proficiency 21 113 3 35 113 5 35 179 1 35 204 6 50 179 2 77 148 6 77 179 6 Primary key There are three relations in second normal form(2NF). The attributes of all relations are fully dependent on the primary key's. Proficiency Table in 2NF
- 13. Analysis Of 2NF The following analysis indicates whether the problems are eliminated in 2NF or not. Updating Problem: If the user need to change the name of Accountant Number 35 to “M.Daud” in 1NF, he must change the name in every record in which Accountant Number 35 appears. But in 2NF, the record of one accountant appears only once. The updating problem eliminated in 2NF. Inconsistent Data: The record of one accountant appears only once in the database, the possibility of inconsistent data is automatically eliminated. Addition Problem: In 1NF, it was not possible to enter a new Skill Number until an Accountant with that skill existed. In 2NF, Any number of skills can be added in skill relation with out an accountant with that skill. It eliminates the addition problem. Deletion Problem: In 2NF, if the record of Ali is deleted, it does not delete any other record.
- 14. Transitive Dependency(def) Transitive dependency is a condition in which an attribute is dependent on an attribute that is not part of primary key. Suppose A, B and C are attributes of a relation. If A approach to B and B approach to C then C is transitively dependent on A through B provided that A is not functionally dependent on B or C. In third Normal Form(3NF) we remove Transitive dependency.
- 15. 3rd Normal Form The Requirements All requirements for 2nd NF must be met. Remove all attributes from the 2NF record that depend on another non-key field. Place them into a new relation with the another attribute as the primary key. The Accountant table in 2NF, contain some attributes which are depending on non-key attributes. For example, Group City and Group Supervisor are depending on a non-key field Group Number. A new relation can be created as;
- 16. Accountant Number Accountant Name Accountant Age Group Number 21 Ali 55 52 35 Daud 32 44 50 Chohan 40 44 77 Zahid 52 52 Primary Key The second table created form the Accountant table in 1NF is as follows: Group Number Group Supervisor 52 Baber 44 Ali Both Accountant table and Group table contain the attribute is used to join both tables. The skill table in 2NF contain no attribute, which is depending on a non-key attribute. It is already in 3NF and will be used with out any further change. Primary Key Skill Table in 3NF Accountant Table in 3NF
- 17. Accountant number Skill Number Proficiency 21 113 3 35 113 5 35 179 1 35 204 6 50 179 2 77 148 6 77 179 6 Primary Key Proficiency Table in 3NF
- 18. Conclusion • We have seen how Database Normalization can decrease redundancy, increase efficiency and reduce anomalies by implementing three of seven different levels of normalization called Normal Forms. The first three NF’s are usually sufficient for most small to medium size applications.