Characteristics of Database Relation and Table in DBMS

Characteristics of Database Tables: A relational database consists of a collection of tables. Each table has 1) a heading or definition part and 2) a body or content part. The heading part consists of the table name and the column names. For example, a student table may have columns for social security number, name, street address, city, state, zip, class, major and GPA. The body shows the rows of the table. Each row in a student table represents a student enrolled at a university.
Once you have created entities representing the business objects you want to represent in your database, you need to create tables to store the data in the database. Tables are made up of rows and columns. Each column corresponds to an attribute of the entity to which the table refers. Every row represents an instance of the entity described by the database table. Specific data relating to each attribute is stored in the rows corresponding to each column.

• Relational Notation in contrast to Database Tables: The difference between a relational notation and a database table is like the difference between a blueprint and a building.
  1. A Plan is similar to the Relational Notation in the ERD diagram.
  2. The implementation is the creation of the database table in the relational database management system.
  
  The following diagram shows a table that contains information about personal computers and points out the components of the table. Each of the red circles highlights each of the attributes.
  

  

A number of characteristics distinguish the database approach from the much older approach of programming with files. In traditional file processing, each user defines and implements the files needed for a specific software application as part of programming the application. For example, one user, the grade reporting office, may keep files on students and their grades. Programs to print a student's transcript and to enter new grades are implemented as part of the application. A second user in the accounting office, may keep track of student's fees and their payments. Although both users are interested in data about students, each user maintains separate files and programs to manipulate these files because each requires some data which may not be available from the other user's files. This redundancy in defining and storing data results in wasted storage space and in redundant efforts to maintain common up-to-date data. In the database approach, a single repository maintains data that is defined once and then accessed by various users. In file systems, each application is free to name data elements independently. In contrast, in a database, the names or labels of data are defined once, and used repeatedly by queries, transactions, and applications. The main characteristics of the database approach versus the file-processing approach are the following:

1. Self-describing nature of a database system
2. Insulation between programs and data, and data abstraction
3. Support of multiple views of the data
4. Sharing of data and multiuser transaction processing

A relational database management system (RDBMS) is a term used to describe a set of programs for both managing a relational database and communicating with that relational database engine. Sometimes front-end tools and complete management kits are included with relational database packages. Microsoft Access is tightly integrated with programming languages such as VB.net. Both the relational database and front-end development tools used to build input screens, are all packaged within the same piece of software. In other words, an RDBMS represents both the database engine and any other tools that come with it. RDBMS is just another name for a relational database product such as Oracle.

• Designing Database Tables: In order for a relational database to function properly, table rows and columns must follow a number of rules grounded in the mathematical discipline of set theory. ^[1] The next few lessons review those rules (in non-mathematical language whenever possible), but for now it is enough to know that the rules exist and that they are practical. Because relational databases are based on set theory, you may encounter the formal terms for database tables and their components in the literature of set theory. Here are the terms you are most likely to see:
  1. Database Tables are referred to as relations.^[2]
  2. The columns of a table are referred to as attributes^[3] or fields^[4].
  3. Rows are referred to as tuples^[5](pronounced tup-pulls) or records^[6].

The term relational database comes from the mathematical term relation (the definition of a two-dimensional table), not the fact that tables can have relationships between them.
Types of Tables

Relational Table Characteristics - Quiz

Terms