QUESTIONS AND CORRECT DETAILED ANSWERS
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Q1: What is a domain in the relational model? - CORRECT ANSWER- A: A domain is a
set of atomic values that defines the type of values that can appear in each
column of a relation.
Q2: What are the six fundamental operations in relational algebra? - CORRECT
ANSWER- A: Selection, Projection, Cartesian Product, Union, Difference, and
Renaming.
Q4: What is the primary difference between BCNF and 3NF? - CORRECT ANSWER- A:
BCNF insists that every non-trivial, irreducible functional dependency has a
candidate key as its determinant, while 3NF allows dependencies where the
dependent attribute is part of the primary key.
Q5: What does the acronym ACID stand for in transactions? - CORRECT ANSWER- A:
Atomicity, Consistency, Isolation, Durability.
,Q6: What is the purpose of normalization in database design? - CORRECT ANSWER- A:
To eliminate redundancy and ensure data integrity by organizing data into normal
forms like 1NF, 2NF, 3NF, and BCNF
Q7: Describe the SELECT statement in SQL. - CORRECT ANSWER- A: The SELECT
statement is used to query data from a database and is typically written as SELECT
columns FROM table WHERE condition.
Q8: What is a foreign key in SQL? - CORRECT ANSWER- A: A foreign key is an attribute
or a set of attributes in one table that refers to the primary key in another table,
ensuring referential integrity.
Q9: What is the difference between static and dynamic hashing? - CORRECT
ANSWER- A: Static hashing has a fixed address space, while dynamic hashing allows
the hash table to grow or shrink dynamically as data is added or removed.
Q10: In the context of functional dependencies, what is meant by the term
"closure"? - CORRECT ANSWER- A: Closure is the set of all attributes that can be
functionally determined from a given set of attributes under a set of functional
dependencies.
Q11: Which of the following commands will add a column email to an existing
table users?
a) ALTER TABLE users ADD email VARCHAR(100);
b) MODIFY TABLE users ADD email VARCHAR(100);
c) ADD COLUMN email VARCHAR(100) TO users;
, d) ALTER users ADD email VARCHAR(100); - CORRECT ANSWER- Correct Answer: a
Q13: Given a table employees with columns name and department, what does
the following query do?
SELECT DISTINCT department FROM employees;
a) Retrieves the count of employees in each department.
b) Retrieves all departments, including duplicates.
c) Retrieves unique department names without duplicates.
d) Retrieves all employee names in each department. - CORRECT ANSWER- Correct
Answer: c
Q12: If the functional dependency A -> B holds, which of the following is true?
a) B can determine A.
b) A uniquely determines B.
c) A and B are independent.
d) A depends on B. - CORRECT ANSWER- Correct Answer: b
Q14: What is the primary purpose of the JOIN clause in SQL?
a) To create new tables dynamically.
b) To delete rows from multiple tables.
c) To filter data from a single table.
d) To combine data from two or more tables based on a related column. - CORRECT
ANSWER- Correct Answer: d