What is a self join? MCQ with Answer and Explanation

What is a self join?

A. Joining tables without a common column

B. Joining more than two tables

C. Joining a table with itself

D. Joining two different tables

Answer: Option C

A self join is a join where a table is joined with itself, often used to compare rows within the same table.

This question belongs to: Computer Database Management System (DBMS)

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Question #1 Report Error

Which of the following is a DML statement?

A. DROP

B. UPDATE

C. ALTER

D. CREATE

Correct Answer: Option B

Explanation:
UPDATE is a Data Manipulation Language (DML) command used to modify existing records in a table. CREATE, ALTER, DROP are DDL.

This question belongs to: Computer Database Management System (DBMS)

Question #2 Report Error

What is the purpose of the SQL GROUP BY ... HAVING combination?

A. To join groups

B. To sort groups

C. To filter groups based on aggregate values

D. To select individual rows

Correct Answer: Option C

Explanation:
HAVING is used in conjunction with GROUP BY to filter groups based on conditions applied to aggregate functions.

This question belongs to: Computer Database Management System (DBMS)

Question #3 Report Error

Which language is used to define the structure of a database, such as creating tables and constraints?

A. DML

B. DDL

C. DCL

D. TCL

Correct Answer: Option B

Explanation:
Data Definition Language (DDL) is used to define and modify the database schema, including CREATE, ALTER, and DROP statements.

This question belongs to: Computer Database Management System (DBMS)