BCS Database Management Systems 2

Question 1

What does SQL JOIN do?

Accepted Answer

Combines rows from two or more tables based on a related column

Answer

A JOIN clause combines rows from two or more tables based on a matching condition between related columns, typically primary and foreign key pairs.

Question 2

What is the difference between DELETE and TRUNCATE in SQL?

Accepted Answer

DELETE removes specific rows with a WHERE clause and is logged; TRUNCATE removes all rows and is faster

Answer

DELETE removes specific rows (or all rows) with transaction logging, while TRUNCATE removes all rows more efficiently by deallocating data pages and cannot be filtered with WHERE.

Question 3

What is an index in a database?

Accepted Answer

A data structure that improves the speed of data retrieval at the cost of additional storage space

Answer

A database index is a data structure (like a B-tree) that allows faster row lookup on indexed columns at the cost of extra storage and slower write operations.

Question 4

In relational algebra, what does the PROJECTION operation do?

Accepted Answer

Selects specific columns from a relation

Answer

The PROJECTION operation (π) selects specific columns from a relation, eliminating all other attributes from the result.

Question 5

What is a stored procedure in a database?

Accepted Answer

A precompiled set of SQL statements stored in the database that can be executed as a single unit

Answer

A stored procedure is a precompiled collection of SQL statements stored in the database that can be called by name, improving performance and code reuse.

BCS - Bachelor Of Computer Science Degree Practice Test

BCS - Bachelor Of Computer Science Degree Practice Test

BCS Database Management Systems 2