Lecture 3: OLAP Business Databases

Question 1

What is a Data Lake?

Answer 1

A database that holds raw data in its narrative form. Copies everything that might be relevant.

(Schema on read)

Question 2

Name one ETL data conversion example?

Answer 2

Date and time conversion.

Question 3

Name one ETL cleaning example?

Answer 3

Garbine in = garbage out (GIGO)

Question 4

Which two ETL load options are there?

Answer 4

1: Integral load (all records taken and compared with
records in DWH, delete and load).

2: Delta/incremental load (only changed records are
taken and processed).

Question 5

Why use OLAP?

Answer 5

Powerful and intuitive way to explore large amounts of data.

Questions are multi-dimensional.

Answers simple and complex business questions.

Question 6

Where does multi-dimensional data consists of?

Answer 6

Measures

Dimensions

Question 7

What is an data measure?

Answer 7

Summable information concerning a business process.

Question 8

What is an data dimension?

Answer 8

Representing the different perspectives.

Year, month

Question 9

Which four OLAP operators are there?

Answer 9

Roll-up
Drill-down
Slice & Dice
Pivot (Rotate)

Question 10

For multi-dimensional modeling you can use two types of schemas, which one?

Answer 10

Star schema

Snowflake schema`

Question 11

What is a star schema?

Answer 11

A fact table in the middle connected to a set
of dimension tables.

(Not normalized)

Question 12

What is a snowflake schema?

Answer 12

A refinement of star schema where
some dimensional hierarchy is normalized into a set of
smaller dimension tables, forming a shape similar to
snowflake

(Normalized)