Database normalization is the cornerstone of database theory. Once a database is normalized, relationships between the data in multiple tables must be established. This comprehensive book assembles concepts and results in relational databases theory previously scattered through journals, books, conference proceedings, and technical memoranda in one convenient source. Book Description. The book is intended for a second course in databases, but is an excellent reference for researchers in the field. In plain terms, his relational database solution provided a level of data independence that allowed users to access information without having to master details of the physical structure of a database. As exciting as the theory was to the technical community, it was still a theory. It needed to be thoroughly tested to see if and how it worked. Relational Database Theory and Logical Design. The present module is focused on Logical Design. The learner will be able to create an Relational Model from the entity-relationship diagram. 3 hours to complete. 2 videos (Total 12 min) See All. Concepts of the.
David Maier’s “The Theory of Relational Databases” is available for free from his website. You can download each chapter in pdf format. This comprehensive book assembles concepts and results in relational databases theory previously scattered through journals, books, conference proceedings, and technical memoranda in one convenient source.
Book Description
The book is intended for a second course in databases, but is an excellent reference for researchers in the field. The material covered includes relational algebra, functional dependencies, multivalued and join dependencies, normal forms, tableaux and the chase computation, representation theory, domain and tuple relational calculus, query modification, database semantics and null values, acyclic database schemes, template dependencies, and computed relations. The final chapter is a brief survey of query languages in existing relational systems. Each chapter contains numerous examples and exercises, along with bibliographic remarks.
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Author(s): David Maier
Publisher: Computer Science Press Format(s): PDF Number of pages: 656 Link: Download.
Building a system in Oracle or some other relational database product does not automatically make it a relational database. Similarly, you can design a perfectly good relational database and implement it in something other than a relational database product. We discuss two important areas:
What makes a database “relational”?
When a database is described as relational, it has been designed to conform (at least mostly) to a set of practices called the rules of normalization. A normalized database is one that follows the rules of normalization.
For example, in an organization, you have employees who work in specific departments. Each employee and department has a number and a name. You could organize this information as shown in Table 1.
Table 1: Sample Employee Information
If you structure your data this way and make certain changes to it, you’ll have problems. For example, deleting all the employees in the Purchasing department will eliminate the department itself. If you change the name of the Marketing department to “Advertising,” you would need to change the record of each employee in that department.
Discovery 3 3rd row seats. Using the principles of relational databases, the Employee and Department data can be restructured into two separate tables (DEPT and EMP), as shown in Tables 2 and 3.
Table 2: A Sample Relational DEPT Table
Table 3: A Sample Relational EMP Table
By using this structure, you can examine the EMP table to find out that Doug works in department 20. Then you can check the DEPT table to find out that department 20 is Purchasing. You might think that Table 1 looks more efficient. However, retrieving the information you need in a number of different ways is much easier with the two-table structure. Joining the information in the two tables for more efficient retrieval is exactly the problem that relational databases were designed to solve.
When the tables are implemented in the database, the information in the two tables is linked by using special columns called foreign keys. In the example, the DeptNo column is the foreign key linking the Department and Employee tables.
Tables 4 and 5 show another common database structure, namely a purchase order (PURCH_ORDER table) for an item and the information details associated with the purchase order (PURCH_ORDER_DTL table).
Table 4: A Sample Relational PURCH_ORDER Table
Relational Database Examples
Table 5: A Sample Relational PURCH_ORDER_DTL Table Maya 2014 – professional 3d modeling and animation tool.
A purchase order can include many items. Table 5 shows that Purchase Order 451 includes three separate items. The link (foreign key) between the tables is the Purchase Order Number.
Understanding basic database terminology
A database consists of tables and columns, as described in the preceding section. There are some other terms you need to know in order to understand how databases work. A database is built in two stages. First you create a logical data model to lay out the design of the database and how the data will be organized. Then you implement the database according to the physical data model, which sets up the actual tables and columns. Different terminology applies to the elements of the logical and physical designs. In addition, relational database designers use different words from object-oriented (OO) database designers to describe the database elements. Table 6 shows the words used in each of these cases.
Relational Database Theory Tutorial
Table 6: Database Design Terminology
The definitions of the words in Table 6 are as follows:
One additional important concept to understand when dealing with relational databases is the primary key. A primary key uniquely identifies a specific instance of an entity. No two instances of an entity can have the same primary key. The values of all parts of the primary key must never be null. The most common types of primary keys in relational databases are ID numbers. For example, in Table 3, the EmpID can be the primary key. Chatty for facebook 1 9 1. Sometimes more than one attribute (or sets of attributes) can be used as a primary key. These attributes are called candidate keys, one set of which must be designated as the primary key.
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