Question 1

What does ACID stand for in database transactions?

Accepted Answer

Atomicity, Consistency, Isolation, Durability. ACID ensures reliable transactions: Atomicity (all or nothing), Consistency (valid state), Isolation (concurrent transactions don't interfere), Durability (committed data persists).

Question 2

What is a primary key?

Accepted Answer

A column (or set of columns) that uniquely identifies each row. A primary key uniquely identifies each record. It cannot be NULL and must be unique. A table can have only one primary key.

Question 3

What is normalization in DBMS?

Accepted Answer

Organizing data to reduce redundancy and improve integrity. Normalization decomposes tables to minimize data redundancy and prevent update anomalies. Normal forms: 1NF, 2NF, 3NF, BCNF.

Question 4

What does a FOREIGN KEY constraint enforce?

Accepted Answer

Referential integrity between two tables. A foreign key ensures that a value in one table corresponds to an existing value in another table's primary key. This enforces referential integrity.

Question 5

Which SQL JOIN returns all rows from both tables, with NULLs where there is no match?

Accepted Answer

FULL OUTER JOIN. FULL OUTER JOIN returns all rows from both tables. Matched rows have data from both; unmatched rows have NULL for the missing side.

DBMS MCQ Quiz

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