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A database is a set of data. But, is the data kept in a database trustworthy? To answer that query we must first answer the question. What is integrity?
Integrity simply means to keep the consistency of data. Therefore, integrity constraints in a database make sure that changes made to the database by authorised users do not compromise data consistency. Therefore, integrity constraints do not permit damage to the database.
There are primarily two integrity constraints: the referential integrity constraint and the entity integrity constraint. In order to describe these two, let us first describe the term Key with respect to a Database Management System.
What Is Recovery? During the life of a transaction, i.e., a after the start of a transaction but before the transaction commits, various changes may be made in a database state
Example: //REVOKE ALL ON EMP FROM MCA12; (All permissions will be cancelled) You can also cancel only some of the permissions. Drop: A user-
Define decision tree classifiers? As the name suggests decision tree classifiers use a tree: Every leaf node has an associated class, and every internal node has a predicate as
Write short note on Events Events consist of inputs, interrupts, decisions and actions performed by any external device or users. Every event always has a sender and receiver.
Which model is record based logical model? Network Modelis basically known as record based logical model.
Define Atom of domain relational calculus An atom has the outline 1 , x 2 , ... , x n > -> r , in which r stands for a relation on n attributes and x 1 , x 2 , ... , x n ar
Write a query that display ename annual salary and comm from emp table
What is known as a search key? An attribute or set of attributes used to look up records in a file is known as a search key.
Define Database layer? The database layer defines the data formats used in the database.
What are axioms? Axioms or rules of inference give a simpler technique for reasoning about
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