Relational Database Model

What does a relational database model primarily represent data as?

• Graphs

• Objects

• Tables

• XML

Which of the following best describes a Natural Join?

• Combines tables based on all columns having the same names and data types

• Combines tables only if their primary keys have identical names

• Combines tables based on the Cartesian product

• Combines tables based on an explicitly specified condition

What describes the result of a Cartesian PRODUCT in relational algebra?

• All possible pairs of rows from two tables

• A subset of rows based on a condition

• A union of two tables with duplicate rows removed

• Rows that match a join condition across two tables

What type of JOIN returns rows where there is at least one match in both tables?

• INNER JOIN

• LEFT OUTER JOIN

• RIGHT OUTER JOIN

• FULL OUTER JOIN

Which of the following is true about foreign keys?

• They uniquely identify each row in any table.

• They can be used to represent relationships between tables.

• They must be unique within a table.

• They eliminate the need for a primary key.

Which of the following operations yields all values for selected attributes, essentially creating a vertical subset of the table?

• SELECT

• PROJECT

• UNION

• JOIN

What is the result of the INTERSECT operation in relational algebra?

• It yields all rows unique to the first table

• It yields rows that appear in either of the tables

• It yields only the rows that appear in both tables

• It yields all rows from both tables without duplication

What does a RIGHT OUTER JOIN do?

• Returns all rows from the left table, and the matched rows from the right table

• Returns all rows from the right table, and the matched rows from the left table

• Returns only the rows from both tables where there is a match

• Returns all rows from both tables, regardless of a match

Referential Integrity Constraint ensures which of the following?

• Each non-null foreign key value references an existing primary key in another table

• All primary keys contain only numeric data

• Data is replicated across multiple tables to avoid data loss

• Foreign keys must uniquely identify records in the same table

A Theta JOIN in relational databases:

• Is based on equality conditions only

• Can only use less than and greater than as operators

• Uses a comparison operator other than equality

• Is not a valid JOIN operation