Database Questions and Answers – OLAP

This set of Database Multiple Choice Questions & Answers (MCQs) focuses on “OLAP”.

1. OLAP stands for
a) Online analytical processing
b) Online analysis processing
c) Online transaction processing
d) Online aggregate processing

Explanation: OLAP is the manipulation of information to support decision making.

2. Data that can be modeled as dimension attributes and measure attributes are called _______ data.
a) Multidimensional
b) Singledimensional
c) Measured
d) Dimensional

Explanation: Given a relation used for data analysis, we can identify some of its attributes as measure attributes, since they measure some value, and can be aggregated upon.Dimension attribute define the dimensions on which measure attributes, and summaries of measure attributes, are viewed.

3. The generalization of cross-tab which is represented visually is ____________ which is also called as data cube.
a) Two dimensional cube
b) Multidimensional cube
c) N-dimensional cube
d) Cuboid

Explanation: Each cell in the cube is identified for the values for the three dimensional attributes.

4. The process of viewing the cross-tab (Single dimensional) with a fixed value of one attribute is
a) Slicing
b) Dicing
c) Pivoting
d) Both Slicing and Dicing

Explanation: The slice operation selects one particular dimension from a given cube and provides a new sub-cube. Dice selects two or more dimensions from a given cube and provides a new sub-cube.

5. The operation of moving from finer-granularity data to a coarser granularity (by means of aggregation) is called a ________
a) Rollup
b) Drill down
c) Dicing
d) Pivoting

Explanation: The opposite operation—that of moving fromcoarser-granularity data to finer-granularity data—is called a drill down.
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6. In SQL the cross-tabs are created using
a) Slice
b) Dice
c) Pivot
d) All of the mentioned

Explanation: Pivot (sum(quantity) for color in (’dark’,’pastel’,’white’)).

7.

`{ (item name, color, clothes size), (item name, color), (item name, clothes size), (color, clothes size), (item name), (color), (clothes size), () }`

This can be achieved by using which of the following ?
a) group by rollup
b) group by cubic
c) group by
d) none of the mentioned

Explanation: ‘Group by cube’ is used .

8. What do data warehouses support?
a) OLAP
b) OLTP
c) OLAP and OLTP
d) Operational databases

Explanation: None.

9.

```SELECT item name, color, clothes SIZE, SUM(quantity)
FROM sales
GROUP BY rollup(item name, color, clothes SIZE);```

How many grouping is possible in this rollup?
a) 8
b) 4
c) 2
d) 1

Explanation: { (item name, color, clothes size), (item name, color), (item name), () }.

10. Which one of the following is the right syntax for DECODE?
a) DECODE (search, expression, result [, search, result]… [, default])
b) DECODE (expression, result [, search, result]… [, default], search)
c) DECODE (search, result [, search, result]… [, default], expression)
d) DECODE (expression, search, result [, search, result]… [, default])

Explanation: None.

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