DBMS

What is a relation in the context of relational databases?

• A table with no rows

• A table with only one column

• A table consisting of rows and columns

• A table with only one row

Which of the following is a basic operation of relational algebra?

• Sorting

• Filtering

• Projection

• Joining

Which of the following is not an extended relational algebra operation?

• Aggregate functions

• Intersection

• Projection

• Outer Join

What does the operation σ (sigma) represent in relational algebra?

• Union

• Selection

• Join

• Projection

A tuple relational calculus query returns:

• A boolean value

• A set of tuples

• A string

• A numeric value

Which of the following SQL statements is used to modify existing data in a table?

• INSERT

• UPDATE

• DELETE

• SELECT

What does a NULL value represent in a database?

• 0

• Empty string

• No data or missing value

• A unique value

Which of the following SQL operations combines two or more queries into one result?

• JOIN

• UNION

• INTERSECT

• MERGE

What is a 'view' in SQL?

• A temporary table

• A stored procedure

• A virtual table derived from a query

• A table created for backup

Which SQL command is used to create a new table in the database?

• CREATE TABLE

• NEW TABLE

• ADD TABLE

• GENERATE TABLE