ahlawat-ACC321_Normalization-50201112

ahlawat-ACC321_Normalization-50201112 - Reminder: Quiz on...

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Unformatted text preview: Reminder: Quiz on Monday 2/6 Question 2-14, 2-15, 2-27 database integrity Normalization Database Design AHLAWAT 3/20/12 Database Integrity: the database contain accurate, valid data Rule 1. Entity Integrity. Each record in the database must have a unique identifier (i.e., a unique primary key). No two records in the database table can have the same primary key value . Rule 2. Primary Key Integrity. The primary key value cannot be null (empty). Each record must have a value for the primary key field. Rule 3. Domain Integrity. The field values must be from a predefined domain. For example, the Date field must have a date and not any other values. Rule 4. Referential Integrity. Data referenced and stored in related tables must be consistent across the database. For example, a customer address should be the same in any table in which it is referenced. Database Anomalies: 3 types of problems in database tables 1. Deletion Problem. Deleting one record (e.g., customer) causes deletion of other records. 2. Update Problem. Updating one field (e.g., address) requires updating multiple fields. 3. Insertion Problem. Inserting a new field (e.g., customer) is problematic because the primary key is null Example Primary key? Normalization q Normalization is the process of organizing data in a database according to guidelines ( rules ) designed both to protect the data and to make the database more flexible/efficient AHLAWAT 3/20/12 Normalization 2 G o a l 1. eliminate redundant data (for example, storing the same data in more than one tableredundant!) 2. ensure data dependencies make sense (only storing related data in a table). Normalization -- benefits q reduce the amount of space a database consumes q allows for more efficient use of data q avoid problems with modifying data AHLAWAT 3/20/12 Normalization process N o r m a l i z a t i o n The process includes creating tables and establishing relationships between those tables by eliminating two factors: redundancy and inconsistent dependency AHLAWAT Normalization: remove inconsistent dependency N o r m a l i z a t i o n Functional (desirable) dependency: all attributes depend on only the primary key Find out a Customers address? Find out a Customers address?...
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ahlawat-ACC321_Normalization-50201112 - Reminder: Quiz on...

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