Consider a fact table in an OLAP application: Facts(D1, D2, val), where D1 and D2 are its dimension attributes and val is a dependent attribute. Suppose attribute D1 takes 3 values and D2 takes 2 values, and all combinations of these values are present in the table Facts. How many tuples are there in the result of the following query?

GATE DA 2025 Q46: OLAP: rows returned by GROUP BY CUBE(D1, D2)

Database Management and Warehousing
2 marks
MCQ
−2/3 if wrong

Consider a fact table in an OLAP application: $\texttt{Facts(D1, D2, val)}$ , where $\texttt{D1}$ and $\texttt{D2}$ are its dimension attributes and $\texttt{val}$ is a dependent attribute. Suppose attribute $\texttt{D1}$ takes 3 values and $\texttt{D2}$ takes 2 values, and all combinations of these values are present in the table $\texttt{Facts}$ . How many tuples are there in the result of the following query?

SELECT D1, D2, sum(val)
FROM Facts
GROUP BY CUBE (D1, D2);

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Answer: D (official GATE 2025 final answer key)

Concept used: CUBE produces groupings for every subset of the listed dimensions.

First step: CUBE(D1, D2) groups by (D1, D2), (D1), (D2) and (): count the rows each grouping contributes.

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Source: official GATE 2025 DA question paper and final answer key, organised by IIT Roorkee. Question paper · Answer key

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GATE DA 2025 Q46: OLAP: rows returned by GROUP BY CUBE(D1, D2)

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