A Database Management System (DBMS) is a software tool that allows users to store, retrieve, manage, and manipulate data efficiently. It provides a structured way to organize data in databases, ensuring data integrity, security, and accessibility. DBMS supports operations like data insertion, updating, deletion, and querying through a user-friendly interface or programming language (e.g., SQL). It is widely used in applications ranging from small businesses to large-scale systems, enabling efficient data handling and supporting decision-making processes. Examples include MySQL, Oracle, and MongoDB.
33 questions and answers
What is Weak entity set? Explain with suitable example.
The entity set which does not have sufficient attributes to form a primary key is called as Weak entity set.
What do you mean by ‘Ternary Relationship’? Define the concept of aggregation with suitable example.
This is a relationship between three entity types. In the real world there are relationships other than those involving two things. For example, suppose that we want to capture which employees use which skills on which project.
With suitable examples, show how recovery in a database system can be done using Log Files with
Deferred Update Recovery Also called NO-UNDO/REDO
Consider the relation R={A,B,C,D,E,F,G,H,I,J} and the set of functional dependencies: F={AB → C, A → DE, B → F, F → GH, D → IJ}. Decompose R into 3NF.
A→DE, so AB→BDE (Augmentation) AB→C, so AB→ABC (Reflexivity)
What is the difference between a database and a table? Why are entity integrity and referential integrity important in a database?
Difference between database and a table: A table is an object inside a database. A database has tables of data, views, indexes and programs. A database can have 10 or thousands of tables.
Explain two-phase locking protocol.
In a multiprogramming environment where multiple transactions can be executed simultaneously,
Write short notes on the following:
Armstrong’s Axioms: An inference axiom is a rule that states if a relation satisfies certain Functional Dependencies (FDs) then it must satisfy certain other FDs.
Write short notes on the following:
View Serializability Let S and S0 be two schedules with the same set of transactions. S and S0 are view equivalent if the following three conditions are met:
Describe the wait-die and wound-wait protocols for deadlock prevention. Define three concurrency problems: dirty read, non-repeatable read, phantoms.
We can prevent deadlocks by giving each transaction a priority and ensuring that lower priority transactions are not allowed to wait for higher priority transactions (or vice versa).
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