Transactions - Database Management System
Subject and UNIT: Database Management System: Unit III: Transactions
This is the first state of transaction. For example: insertion, deletion or Isubiv updation of record is done here. But data is not saved to database.
Transactions - Database Management System
Subject and UNIT: Database Management System: Unit III: Transactions
This property states that each transaction must be considered as a single unit and must be completed fully or not completed at all.
Transactions - Database Management System
Subject and UNIT: Database Management System: Unit III: Transactions
Definition: A transaction can be defined as a group of tasks that form a single logical unit.
Databases Design - Database Management System
Subject and UNIT: Database Management System: Unit II: Databases Design
The ER data model specifies enterprise schema that represents the overall logical structure of a database.
Databases Design - Database Management System
Subject and UNIT: Database Management System: Unit II: Databases Design
Observe order for many items. Item lines has many attributes-called composite attributes. Each tuple has variable length.
Databases Design - Database Management System
Subject and UNIT: Database Management System: Unit II: Databases Design
Join decomposition is a further generalization of Multivalued dependencies. If the join of R1 and R2 over C is equal to relation R, then we can say that a Join Dependency (JD) exists.
Databases Design - Database Management System
Subject and UNIT: Database Management System: Unit II: Databases Design
The multivalued dependency is denoted by →.If there exists a multivalued dependency then the table is not in 4th normal form.
Databases Design - Database Management System
Subject and UNIT: Database Management System: Unit II: Databases Design
Boyce and Codd Normal Form is a higher version of the Third Normal form. This form deals with certain type of anomaly that is not handled by 3NF.
Databases Design - Database Management System
Subject and UNIT: Database Management System: Unit II: Databases Design
Normalization is the process of reorganizing data in a database so that it meets two basic requirements: 1) There is no redundancy of data (all data is stored in only one place), and 2) data dependencies are logical (all related data items are stored together)
Databases Design - Database Management System
Subject and UNIT: Database Management System: Unit II: Databases Design
Decomposition is the process of breaking down one table into multiple tables.A decomposition of relation Schema R consists of replacing the relation Schema by two relation schema.
Databases Design - Database Management System
Subject and UNIT: Database Management System: Unit II: Databases Design
Definition: Redundancy is a condition created in database in which same piece of data is held at two different places.
Databases Design - Database Management System
Subject and UNIT: Database Management System: Unit II: Databases Design
Definition: Let P and Q be sets of columns, then: P functionally determines Q, written P→Q if and only if any two rows that are equal on (all the attributes in) P must be equal on (all the attributes in) Q.