OLAP

Give an example question that can be answered by OLAP, if we have a database containing employees with the dimensions location, position, and salary.

How do average salaries of salesmen compare to average salaries of vice presidents?

Why is MOLAP faster than ROLAP?

MOLAP uses data structures which are specifically catered to multidimensional data, like multidimensional arrays and the like. These are implicitly indexed, and their retrieval is very quick. They also are able to have the same features with less metadata to consider when querying.

_______ are values that can be aggregated on and are seen within the cube, _______ categorize the data that is inside the cube.

Measure attributes, Dimension attributes

Determine if the following action is slicing, dicing, or drill-up: Viewing a subset of the OLAP cube as another cube.

Dicing.

What does OLAP stand for?

OLAP stands for OnLine Analytical Processing.

Name a product which can be used for OLAP.

Oracle OLAP, SAP, Microsoft Excel, Sybase, Microsoft SQL Server, Essbase.

_______ a two dimensional view of an OLAP cube to see specific values.

Pivot table

Which uses relational tables to keep track of data and metadata, ROLAP or MOLAP?

ROLAP

Given very large data sets, would you choose MOLAP or ROLAP?

ROLAP, if MOLAP was chosen the performance would suffer. ROLAP can handle larger data sets and the input would be faster than MOLAP.

Determine if the following action is drill-down or roll-up: Aggregating data so that it can then be computed in one or more dimensions.

Roll-up.

State whether this set of data can be used for OLAP: A database containing regions, products, and sales.

Since this contains multiple dimensions by which we can identify data, it could be useful to store it in OLAP for analysis

State whether this set of data can be used for OLAP: A database of shoes organized by color, size, and material.

Since this contains multiple dimensions by which we can identify data, it could be useful to store it in OLAP for analysis.

Explain the purpose of slicing an OLAP cube.

Slicing is projecting to a lower dimension. We can extract a 2-dimensional table from a 3-dimensional cube by slicing based on two dimensions and specifying a constant for the third dimension.

True or False: PostgreSQL is capable of performing OLAP-related queries.

True

Do most modern database systems that support OLAP use relational tables, or multidimensional data structures?

Neither; (it's a trick question) most use a hybrid called HOLAP that supports both relational tables and multidimensional tables.

State whether this set of data can be used for OLAP: A back-end database for a car dealership's inventory

While we could use OLAP, it wouldn't be very productive or useful. An inventory database isn't meant for analysis, and is often small enough to keep track of in conventional databases which use relations.

What OLAP term best describes accessing data at a lower level in a structured hierarchical database? a. Roll-up b. Dicing c. Drill-down d. Slicing

c. Drill-down.

State whether this set of data can be used for OLAP: A database of a text-message client containing received and sent messages.

This is not really possible, since text messages generally are just a list of messages. Their only attributes are who sent or received them, and maybe a timestamp, which aren't dimensional attributes.

True or False: OLAP is good for maintaining your sheep farm.

False

True or False: OLAP is good for working with data that is frequently being updated.

False

True or False: OLAP is good storing usernames and passwords on your website.

False

True or False: OLAP performs calculations on its own.

False. OLAP is a method of organizing and retrieving data which is meant to facilitate doing calculations, but does not do any calculations on its own.

State whether this set of data can be used for OLAP: A database containing profile data from a social networking website.

This is possible, and entirely depends on the context. A back-end database which powers Facebook profiles, for example, will most likely be a standard relational database which is interacted with by the front-end (website). But a business-side employee might request data from profiles to build a collection of data which can be used for OLAP.

True or False: OLAP is good for mining large sets of already gathered data in a specific area.

True

Explain what it means to "drill-down" on an OLAP cube.

Drilling down involves changing our level of specificity in a hierarchical attribute. For example, to drill down on time might change our dimension from 'Year' to 'Month.'

When working with an OLAP cube, what does it mean to consolidate?

Consolidation involves aggregating the data and structuring it into a cube. You will be viewing the entire structure when consolidation has completed.

Determine if the following action is drill-down or roll-up: Accessing data that is on a lower level in the hierarchical structured database.

Drill-down.

Determine if the following action is slicing, dicing, or drill-up: Accessing data that is on a higher level in the hierarchical structured database.

Drill-up.

State whether this set of data can be used for OLAP: A database containing products, customers, and sales.

Since this contains multiple dimensions by which we can identify data, it could be useful to store it in OLAP for analysis.

Determine if the following action is slicing, dicing, or drill-up: Projecting an OLAP cube onto a lower amount of dimensions.

Slicing.