A Database Management System (DBMS) enables a company to routinely produce, update, archive, and retrieve a collection of data at a faster rate. Apart from software engineer profiles, DBMS is essential for various data analyst profiles in companies such as impend Analytics, Fractal, latent view analytics etc.
Following is the top DBMS & SQL Placement MCQ questions and answers to help you crack best company placements.
Basic DBMS & SQL Placement Questions
Q1. The domain of an attribute in a relation is
The Relationship between the attributes
set of values that can uniquely identify each tuple of a relation
The set of all permitted values of that attribute
Property of an entity set
Correct Answer: c The set of all permitted values of that attribute
The domain of an attribute is the set of all values permitted for that attribute. It defines the range of values that an attribute in a relation can take. It is used to constrain the values of an attribute to ensure data integrity.
Q2. The logical structure or blueprint of the database is called
Correct Answer: c Database Schema
The database schema explains the construction and structure of the database. It contains the information about the tables, indexes, views, etc., in a database. So, the correct answer is Database Schema
Q3. The COLLATE operator in SQL is used to
change the data type of an attribute
sort the data in the table according to the specified collation
combine all the data in a table and store it in a file
sort the tuples in a relation in alphabetical order
Correct Answer: b sort the data in the table according to the specified collation
The set of rules used to compare the characters or strings in a database is called collation. The COLLATE clause in SQL is used to sort the strings according to the specified collation.
Q4. An enum field can take how many different values at the maximum?
Correct Answer: d 65535
Q5. Which of the following is an example of derived attribute?
Date of Joining
Correct Answer: d Experience
An attribute which is derived from another attribute is called a derived attribute. In the given ER diagram, the ‘Experience’ attribute can be derived from the ‘Date of Joining’ attribute. Hence, ‘experience’ is the derived attribute.
Q6. Which SQL statement is used to remove all the tuples from a relation?
All the above
Correct Answer: c TRUNCATE
DROP statement deletes the entire table irrevocably. TRUNCATE is a DDL statement that is used to delete all the tuples in the table, preserving the structure of the table.
Q7. Which of the following statements can be used to get a name which starts with ‘D’ and ends with ‘i’ using LIKE clause in SQL?
Correct Answer: a LIKE ‘d%i’
Explanation: The SQL LIKE operator is used to search for a specific pattern in a string.
% represents one or more characters.
_ represents a single character.
So, the correct answer is LIKE ‘d%i’. Because, it represents the pattern which starts with ‘d’, has one or more characters in between and ends with ‘i’.
Q8. A relation is in 3NF if
Every non-prime attribute is functionally dependent on the primary key
Every prime attribute is functionally dependent on a non-prime attribute
Some non-prime attributes are functionally dependent on the primary key
If all the functional dependencies have a super key on their right side
Correct Answer: a Every non-prime attribute is functionally depend to the primary key
The third normal form removes transitive dependency from the table. For a relation satisfy 3NF, either LHS should be a super key or RHS should be prime attribute in every FD of the relation.
Q9. The data which provides data about the database is called
Correct Answer: b metadata
Metadata contains the information about the data organization, files, tables etc., in the database. Data about the database is called Metadata. Hence, the correct answer is ‘metadata’.
Q10. Two attributes are functionally dependent if and only if
Together they constitute a composite key
The relation is in third normal form
Together they constitute a foreign key.
Value in one column determines the value of the other column
Correct Answer: a together they constitute a composite key
Certain functional dependencies can be proved to hold on the schema using the given set of functional dependencies. Hence, two attributes that are functionally dependent, form a composite key for the relation.
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