TransactionThe transaction is a set of logically related operations. It contains a group of tasks.A transaction is an action or series of actions. It is performed by a single user to perform operations for accessing the contents of the database.Example: Suppose an employee of a bank transfers Rs 800 from X's account to Y's account. This...
Showing posts with label DBMS. Show all posts
Showing posts with label DBMS. Show all posts
08 April, 2022
Canonical Cover
Canonical CoverIn the case of updating the database, the responsibility of the system is to check whether the existing functional dependencies are getting violated during the process of updating. In case of a violation of functional dependencies in the new database state, the rollback of the system must take place.A canonical cover or irreducible...
Inclusion Dependency
Inclusion DependencyMultivalued dependency and join dependency can be used to guide database design although they both are less common than functional dependencies.Inclusion dependencies are quite common. They typically show little influence on the design of the database.The inclusion dependency is a statement in which some columns of a relation...
Join Dependency
Join DependencyJoin 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.Where R1 and R2 are the decompositions R1(A, B, C) and R2(C, D) of a given relations R (A, B, C, D).Alternatively, R1 and R2 are lossless decompositions...
Multivalued Dependency
Multivalued DependencyMultivalued dependency occurs when two attributes in a table are independent of each other but, both depend on a third attribute.A multivalued dependency consists of at least two attributes that are dependent on a third attribute that's why it always requires at least three attributes.Example: Suppose there is a bike...