BSCS : Database Management Systems 4

Question 1

Which isolation level prevents dirty reads but still allows non-repeatable reads?

Accepted Answer

Read Committed

Answer

Read Committed allows a transaction to only see committed data, preventing dirty reads but permitting non-repeatable reads between queries.

Question 2

In a data warehouse, a fact table typically contains:

Accepted Answer

Quantitative measures and foreign keys to dimensions

Answer

Fact tables store measurable business events (metrics) along with foreign keys that link to dimension tables.

Question 3

What does a FOREIGN KEY constraint enforce?

Accepted Answer

Referential integrity between two tables

Answer

A FOREIGN KEY constraint ensures that a value in the referencing column must exist as a primary or unique key in the referenced table.

Question 4

Which SQL aggregate function returns the number of non-NULL values in a column?

Accepted Answer

COUNT(col)

Answer

COUNT(col) counts only non-NULL values in the specified column, while COUNT(*) counts all rows including those with NULLs.

Question 5

Deadlock in a DBMS occurs when:

Accepted Answer

Two or more transactions wait for each other's locked resources indefinitely

Answer

Deadlock is a cycle of waiting transactions, each holding a resource the next one needs, so none can proceed.

BSCS - Bachelor of Science in Computer Science Practice Test