Fundamental Database Concepts Flashcards

What is the primary purpose of database normalization?

Answer: To reduce data redundancy and improve data integrity

Normalization organizes data to minimize redundancy and dependency, preventing update, insert, and delete anomalies.

In an Entity-Relationship (ER) diagram, what does a diamond shape represent?

Answer: A relationship

In ER diagrams, diamond shapes represent relationships (associations) between entities, while rectangles represent entities and ovals represent attributes.

What is a non-correlated subquery?

Answer: A subquery that executes independently of the outer query

A non-correlated subquery executes once independently and passes its result to the outer query, unlike a correlated subquery which references outer query columns.

Which Oracle SQL function returns the current date and time including fractional seconds and timezone?

Answer: SYSTIMESTAMP

SYSTIMESTAMP returns the current date and time including fractional seconds and the database timezone, while SYSDATE returns only date and time without fractional seconds.

What is a composite primary key?

Answer: A primary key composed of two or more columns together

A composite primary key uses multiple columns in combination to uniquely identify each row, where no single column alone provides uniqueness.

What does the term 'schema' refer to in Oracle Database?

Answer: A collection of database objects owned by a database user

In Oracle, a schema is the collection of all objects (tables, views, indexes, sequences, etc.) that belong to a particular database user.

Which type of database model stores data in nodes connected by edges, making it ideal for social networks?

Answer: Graph model

A graph database model uses nodes (entities) and edges (relationships) to store data, excelling at traversing complex relationship networks like social graphs.