Database Views and Semantic Constraints

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Questions and Answers

What is the primary purpose of a view in a database?

To increase the storage capacity of a database
To permanently delete data from tables
To directly manage user permissions
To present data without modifying underlying tables (correct)

Which of the following is NOT a type of semantic constraint?

Data Redundancy Rules (correct)
Domain Constraints
Referential Integrity
Assertions

What SQL command is used to create a view named 'TopStudents'?

CREATE VIEW TopStudents AS SELECT StudentDetails.S_ID, StudentDetails.NAME, StudentMarks.MARKS FROM StudentDetails JOIN StudentMarks ON StudentDetails.S_ID = StudentMarks.ID WHERE StudentMarks.MARKS > 80 (correct)
CREATE VIEW TopStudents AS INSERT INTO StudentMarks
CREATE VIEW TopStudents AS DELETE FROM StudentDetails
CREATE VIEW TopStudents AS SELECT * FROM Students

What occurs when a semantic constraint of 'CHECK (MARKS BETWEEN 0 AND 100)' is in place?

It enforces that MARKS can only be integers between 0 and 100 (C) Signup and view all the answers

What is the role of triggers in a database?

To perform automatic actions based on specific events (D) Signup and view all the answers

Which statement accurately describes how triggers operate?

Triggers can be defined to fire either before or after a database event (D) Signup and view all the answers

Which of the following examples illustrates a proper use of a view?

CREATE VIEW AllStudents AS SELECT * FROM StudentMarks WHERE MARKS < 50 (C) Signup and view all the answers

How do domain constraints function in a database?

They enforce limits on the types of data that can be entered (A) Signup and view all the answers

Study Notes

Views are virtual tables that simplify complex queries, organize data without altering underlying tables, and allow users to focus on relevant information, restrict access, and simplify joins. Example: `CREATE VIEW TopStudents AS SELECT StudentDetails.S_ID, StudentDetails.NAME, StudentDetails.ADDRESS, StudentMarks.MARKS FROM StudentDetails JOIN StudentMarks ON StudentDetails.S_ID = StudentMarks.ID WHERE StudentMarks.MARKS > 80;`.

Semantic Constraints ensure data integrity. Types include Domain Constraints (data type limits), Referential Integrity (consistent table relationships), and Assertions (truth conditions for rows). Example: CREATE TABLE StudentMarks (ID INT PRIMARY KEY, NAME VARCHAR(50), MARKS INT, AGE INT, CONSTRAINT chk_marks CHECK (MARKS BETWEEN 0 AND 100));

Triggers are procedures that execute automatically on database events (INSERT, UPDATE, DELETE) to maintain data integrity and enforce rules.

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Description

This quiz explores the concepts of views in databases and their role in simplifying complex queries. It also covers semantic constraints that ensure data integrity through various types of constraints. Test your understanding of how these elements function within a database structure.