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17 Questions

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Oracle APEX Page Creation Process

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Questions and Answers

Which operation in relational algebra allows for selecting a subset of rows based on certain conditions?

Set difference

Selection (correct)

Cartesian product

Projection

What does the UNION operation in relational algebra do?

Discard duplicates from the result

Tuples in R1, but not in R2

Combine two relations (correct)

Select a subset of rows from a relation

In grouping data, what does the GROUP BY clause do?

Produces a single summary row for each group (correct)

Selects the maximum value in a group

Orders the groups based on a specified criteria

Adds additional fields to the projection list

Which statement about GROUP BY in SQL is correct?

GROUP BY may contain all the GROUP BY expressions Signup and view all the answers

When adding additional fields to the projection list, what must be done in SQL?

Include them in the GROUP BY clause Signup and view all the answers

What are the conditions that a primary key should satisfy?

Is representative in the problem context Signup and view all the answers

What is the purpose of a foreign key in a relational database?

To link two tables by referencing the primary key of one table in another Signup and view all the answers

How is referential integrity ensured when inserting a record in a secondary table?

By ensuring that the corresponding key exists in the referenced table Signup and view all the answers

What is a common solution to handling deadlocks in relational databases?

Using late checking of constraints Signup and view all the answers

What is the purpose of integrity constraints in a database schema?

To ensure that logical expressions are satisfied by any instance of the database Signup and view all the answers

In database design, what is the function of a primary key?

To ensure uniqueness of tuples in a relation Signup and view all the answers

What is the difference between a key and a superkey in the context of relational databases?

A key ensures uniqueness, while a superkey includes at least one key Signup and view all the answers

At which level of abstraction is the data described in terms of its physical storage and location?

Physical level Signup and view all the answers

What does the term "cardinality" refer to in the context of a relational database?

The number of distinct records in a relation Signup and view all the answers

In the context of a relational database, what is the "degree" of a relation?

The number of attributes in a relation Signup and view all the answers

What is the primary purpose of an integrity constraint in a relational database?

To enforce data integrity rules Signup and view all the answers

When setting up referential integrity between two tables, what does the foreign key in one table typically refer to?

Primary key in another table Signup and view all the answers