Complete Notes on RDBMS

Following are three levels of data abstraction: Physical level: It is the lowest level of abstraction. It describes how data are stored. Logical level: It is the next higher level of abstraction. It describes what data are stored in the database and what the relationship among those data is. View level: It is the highest … Read more

Data abstraction in DBMS is a process of hiding irrelevant details from users. Because database systems are made of complex data structures so, it makes accessible the user interaction with the database. For example: We know that most of the users prefer those systems which have a simple GUI that means no complex processing. So, … Read more

Inconsistent Not secure Data redundancy Difficult in accessing data Data isolation Data integrity Concurrent access is not possible Limited data sharing Atomicity problem The disadvantages of file processing systems include: Data Redundancy: In a file processing system, data redundancy is common because the same data may be duplicated in multiple files. This redundancy can lead … Read more

The Relationship is defined as an association among two or more entities. There are three type of relationships in DBMS- One-To-One: Here one record of any object can be related to one record of another object. One-To-Many (many-to-one): Here one record of any object can be related to many records of other object and vice … Read more

The degree of relation is a number of attribute of its relation schema. A degree of relation is also known as Cardinality it is defined as the number of occurrence of one entity which is connected to the number of occurrence of other entity. There are three degree of relation they are one-to-one(1:1), one-to-many(1:M), many-to-one(M:M). … Read more