What is data redundancy? MCQ with Answer and Explanation
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Question #1
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Which constraint ensures that every value in a specific column is unique across all rows in that table, but still permits a NULL value?
Correct Answer: Option A
Explanation:
The UNIQUE constraint prevents duplicate entries in a column. Unlike a Primary Key, a UNIQUE constraint typically allows one or more rows to store NULL values depending on the database engine.
The UNIQUE constraint prevents duplicate entries in a column. Unlike a Primary Key, a UNIQUE constraint typically allows one or more rows to store NULL values depending on the database engine.
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Computer
Database Management System (DBMS)
Question #2
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Which of the following is an example of a NoSQL database?
Correct Answer: Option D
Explanation:
MongoDB is a document-oriented NoSQL database. PostgreSQL, MySQL, and Oracle are RDBMS.
MongoDB is a document-oriented NoSQL database. PostgreSQL, MySQL, and Oracle are RDBMS.
This question belongs to:
Computer
Database Management System (DBMS)
Question #3
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What is the result of the SQL query: SELECT * FROM employees;?
Correct Answer: Option B
Explanation:
SELECT * retrieves all columns and rows from the specified table.
SELECT * retrieves all columns and rows from the specified table.
This question belongs to:
Computer
Database Management System (DBMS)
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