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DBMS Training & SQL Tutorial :
Introduction to Database Management

apid Theory you need to know!


Database Concepts :

  • A database consists of a number of tables. Each table comprises of rows(records) and columns(attributes). Each record contains values for the corresponding attributes. The values of the attributes for a record are interrelated. For example, different cars have different values for the same specifications (length, color, engine capacity, etc.).

  • In the database oriented approach, we store the common data in one table and access it from the required tables. Thus the redundancy of data decreases.

  • The database oriented approach supports multiple views of the same data. For example, a clerk may only be able to see his details, whereas the manager can view the details of all the clerks working under him.

  • Multiple views of the same database may exist for different users. This is defined in the view level of abstraction.

  • The logical level of abstraction defines the type of data that is stored in the database and the relationship between them.

  • The design of the database is known as the database schema.

  • The instance of the database is the data contained by it at that particular moment.

  • The Database Administrator has the total control of the database and is responsible for the setting up and maintaining the database.

Languages :
  • The DDL (Data Definition Language) is used to define the schema of the database and relations between entities.

  • The DML (Data Manipulation Language) enables us to access and operate upon the data in the database.

  • The DCL (Data Control Language) is used to control the access to the database.

  • The Procedural DML requires the user to state the information required and how to get it whereas the Non-Procedural DML does not require the user to specify how to get the information.

  • The query processor breaks down the DML statements into statements that can be comprehended by the DBMS.

Transaction Management:
  • A transaction is a collection of commands that together perform a particular task. For example, a transaction to transfer funds from one bank account to another includes debiting one account and crediting the other account with the same amount.

  • Transaction Management must satisfy the properties of Atomicity,Consistency,Isolation and Durability (ACID)

  • The property of atomicity in transaction management ensures that either the entire transaction occurs completely or does not occur at all.

  • The property of durability in transaction management ensures that the new values of the database persist across system failures.

  • The storage manager interfaces between the actual data that is stored by the database and the application programs that submit the queries.


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