DMC Database Normalization and Design Patterns

Question 1

What is First Normal Form (1NF) and what does it eliminate?

Accepted Answer

Eliminates repeating groups and multi-valued attributes, ensuring each column holds atomic (single) values

Answer

1NF requires that every column holds a single, indivisible atomic value, eliminating repeating groups, arrays, and nested collections from table columns.

Question 2

What anomaly occurs when deleting a row unintentionally destroys other needed information?

Accepted Answer

Deletion anomaly

Answer

A deletion anomaly occurs when removing a row destroys other data that was stored in the same row but had no logical reason to be deleted.

Question 3

What anomaly occurs when inserting new data requires entering dummy or NULL values for unrelated attributes?

Accepted Answer

Insertion anomaly

Answer

An insertion anomaly occurs when you can't add new data without also supplying values for unrelated attributes that have no current meaning.

Question 4

What is an update anomaly in an unnormalized table?

Accepted Answer

When the same fact is stored in multiple rows and updating one row without updating all causes inconsistency

Answer

An update anomaly occurs when a single logical fact is stored in multiple rows, so updating it in one place without updating all copies creates inconsistent data.

Question 5

What is a join dependency, and which normal form addresses it?

Accepted Answer

A dependency where a table can only be reconstructed losslessly by joining three or more projections — addressed by 5NF (PJNF)

Answer

A join dependency exists when a table can only be decomposed into more than two tables and still be reconstructed losslessly, which Fifth Normal Form (5NF/PJNF) eliminates.

DMC - Data Modeling Certification Practice Test

DMC - Data Modeling Certification Practice Test

DMC Database Normalization and Design Patterns