DBMS MCQ
Table of Contents
What is a Database?
A database is a collection of related data which represents some aspect of the real world. A database system is designed to be built and populated with data for a certain task.
What is DBMS?
Database Management System (DBMS) is a software for storing and retrieving users’ data while considering appropriate security measures. It consists of a group of programs which manipulate the database. The DBMS accepts the request for data from an application and instructs the operating system to provide the specific data. In large systems, a DBMS helps users and other third-party software to store and retrieve data.
DBMS allows users to create their own databases as per their requirement. The term “DBMS” includes the user of the database and other application programs. It provides an interface between the data and the software application.
In this section, we are going to cover some of the basic questions based on DBMS, which are frequently asked during an interview. Here we will try to cover almost all the topics related to DBMS.
21) SELECT * FROM class WHERE marks>90 AND roll_no = 20;
What should be the output for the above query?
A. Marks and roll_no
B. class
C. Marks
D. All the columns from the class table.
Answer: d
Explanation: The “*” character in SQL is used to show all columns of the table.
22) Choose the wrong option in this question.
A. SELECT * FROM table_name WHERE column_name;
B. SELECT column_name FROM table_name;
C. SELECT column_name FROM table_name WHERE condidtion;
D. SELECT column_name WHERE condition;
Answer: d
Explanation: The correct answer is option D because the SELECT command does not produce output without specifying the table name.
23) Which clause is used to extract only those records that fulfill a specified condition?
A. SELECT
B. WHERE
C. FROM
D. ALL
Answer: b
24) INSERT INTO employee ……(101,xyz,5000);
What keyword is missing in the given statement?
A. table
B. values
C. column
D. field
Answer: b
Explanation: To insert value in the table, we have to use the INSERT keyword with the VALUES clause.
25) Which of the following condition allow to join relations?
A. Set
B. Where
C. Using
D. On
Answer: d
Explanation: On condition is used for join expressions.
26) Which of the join operations do not preserve non matched tuples?
A. Left join
B. Inner join
C. Right join
D. Full join
Answer: b
Explanation: Inner join returns all rows from both tables when there is at least one match is found.
27) What type of join is needed when you want to include rows that do not have matching values?
A. Equi-join
B. Natural join
C. Outer join
D. None of the above
Answer: d
Explanation: An outer join does not require each record in the two joined tables to have a matching record.
28) Which joins refer to joining records from the right table with no matching values in the left table?
A. Left join
B. Right join
C. Full join
D. Half join
Answer: b
Explanation: Right join returns all values from the right table and the matched values from the left table.
29) How many tables can be combined with a join?
A. One
B. Two
C. Three
D. Many
Answer: d
Explanation: Join operation can combine many tables at a time.
30) Which join is used to return all tuples from both tables even condition doesn’t satisfy?
A. Inner join
B. Right join
C. Natural Join
D. Full join
Answer: d
Explanation: In a full outer join, all tuples from both relations are included in the result, irrespective of the matching condition.
