Chapter 6 Flashcards
What is normalization
Normalization is the process of efficiently organizing data in a database by splitting a relational table into smaller tables by projection. There are basically two goals of normalization as follows:
- Eliminate redundant data (for example, storing the same data in more than one table)
- Ensuring data dependencies make sense (only storing related data in a table).
What is normal form
The database community has developed a series of guidelines for ensuring that databases are indeed normalized.
How much levels are for normalization
5
What causes update anomalies
Redundancy
What are Update anomalies
Update anomalies are problems that arise when records are inserted, deleted, or updated in the database.
What is 1NF
As per First Normal Form, no two Rows of data must contain repeating group of information i.e each set of column must have a unique value, such that multiple columns cannot be used to fetch the same row.
What kind of denormalization done in dataware housing
Selective
Does OLAP denormalized
yes
Does update operation fast in normalization
Yes
Which normal form actually used in market
Up to 3rd
What are atomic values
The values which are not sum or aggregated. They are in raw form.
What is denormalization
We convert normal from to denormal form. We could take table from 2NF to 1NF. It means it is reverse of normalization
Does DWH normalize data
Yes
What is 2NF
Every non-key column is fully dependent on the PK
What is 3NF
All columns should be functionally dependent
