50 SQL Practice Questions for Good Results in Interview

Hello friends, we’ve brought you 50 SQL query interview questions and answers for practice. Solving practice questions is the fastest way to learn any subject. That’s why we’ve selected a set of 50 SQL queries that you can use to step up your learning.

You can start by running the readymade SQL scripts to create the test data. The script includes a sample Worker table, a Bonus, and a Title table with pre-filled data. Just run the SQL script, and you are all set to get started with the SQL queries. Practice with these SQL queries frequently asked in interviews and get your dream jobs in top IT MNCs like Amazon, Flipkart, Facebook, etc.

We recommend you go through the questions and form queries by yourself. Try to find answers on your own. However, you can’t start until the required sample data is not in place. We have provided an SQL script to seed the test data. Use it first to create a test database and tables.

By the way, we have many other posts available for SQL interview preparation. So if you are interested, then follow the link given below.

Prepare Sample Data To Practice SQL Skills

Sample Table – Worker

Sample Table – Bonus

Sample Table – Title

To prepare the sample data, run the following queries in your database query executor or SQL command line. We’ve tested them with the latest version of MySQL Server and MySQL Workbench query browser. You can download these tools and install them to execute the SQL queries. However, these queries will run fine in any online MySQL compiler, you may use them.

SQL Script to Seed Sample Data.

CREATE DATABASE ORG;
SHOW DATABASES;
USE ORG;

CREATE TABLE Worker (
	WORKER_ID INT NOT NULL PRIMARY KEY AUTO_INCREMENT,
	FIRST_NAME CHAR(25),
	LAST_NAME CHAR(25),
	SALARY INT(15),
	JOINING_DATE DATETIME,
	DEPARTMENT CHAR(25)
);

INSERT INTO Worker 
	(WORKER_ID, FIRST_NAME, LAST_NAME, SALARY, JOINING_DATE, DEPARTMENT) VALUES
		(001, 'Monika', 'Arora', 100000, '21-02-20 09.00.00', 'HR'),
		(002, 'Niharika', 'Verma', 80000, '21-06-11 09.00.00', 'Admin'),
		(003, 'Vishal', 'Singhal', 300000, '21-02-20 09.00.00', 'HR'),
		(004, 'Amitabh', 'Singh', 500000, '21-02-20 09.00.00', 'Admin'),
		(005, 'Vivek', 'Bhati', 500000, '21-06-11 09.00.00', 'Admin'),
		(006, 'Vipul', 'Diwan', 200000, '21-06-11 09.00.00', 'Account'),
		(007, 'Satish', 'Kumar', 75000, '21-01-20 09.00.00', 'Account'),
		(008, 'Geetika', 'Chauhan', 90000, '21-04-11 09.00.00', 'Admin');

CREATE TABLE Bonus (
	WORKER_REF_ID INT,
	BONUS_AMOUNT INT(10),
	BONUS_DATE DATETIME,
	FOREIGN KEY (WORKER_REF_ID)
		REFERENCES Worker(WORKER_ID)
        ON DELETE CASCADE
);

INSERT INTO Bonus 
	(WORKER_REF_ID, BONUS_AMOUNT, BONUS_DATE) VALUES
		(001, 5000, '23-02-20'),
		(002, 3000, '23-06-11'),
		(003, 4000, '23-02-20'),
		(001, 4500, '23-02-20'),
		(002, 3500, '23-06-11');

CREATE TABLE Title (
	WORKER_REF_ID INT,
	WORKER_TITLE CHAR(25),
	AFFECTED_FROM DATETIME,
	FOREIGN KEY (WORKER_REF_ID)
		REFERENCES Worker(WORKER_ID)
        ON DELETE CASCADE
);

INSERT INTO Title 
	(WORKER_REF_ID, WORKER_TITLE, AFFECTED_FROM) VALUES
 (001, 'Manager', '2023-02-20 00:00:00'),
 (002, 'Executive', '2023-06-11 00:00:00'),
 (008, 'Executive', '2023-06-11 00:00:00'),
 (005, 'Manager', '2023-06-11 00:00:00'),
 (004, 'Asst. Manager', '2023-06-11 00:00:00'),
 (007, 'Executive', '2023-06-11 00:00:00'),
 (006, 'Lead', '2023-06-11 00:00:00'),
 (003, 'Lead', '2023-06-11 00:00:00');

Once the above SQL runs, you’ll see a result similar to the one attached below.

Start with 20 Basic SQL Questions for Practice

Below are some of the most commonly asked SQL queries in interviews from various fields. Get a timer to track your progress and start practicing.

Q-1. Write an SQL query to fetch “FIRST_NAME” from the Worker table using the alias name <WORKER_NAME>.

Ans.

The required query is:

Select FIRST_NAME AS WORKER_NAME from Worker;

Q-2. Write an SQL query to fetch “FIRST_NAME” from the Worker table in upper case.

Ans.

The required query is:

Select upper(FIRST_NAME) from Worker;

Q-3. Write an SQL query to fetch unique values of DEPARTMENT from the Worker table.

Ans.

The required query is:

Select distinct DEPARTMENT from Worker;

Q-4. Write an SQL query to print the first three characters of  FIRST_NAME from the Worker table.

Ans.

The required query is:

Select substring(FIRST_NAME,1,3) from Worker;

Q-5. Write an SQL query to find the position of the alphabet (‘a’) in the first name column ‘Amitabh’ from the Worker table.

Ans.

The required query is:

Select INSTR(FIRST_NAME, BINARY'a') from Worker where FIRST_NAME = 'Amitabh';

Notes.

• The INSTR does a case-insensitive search.
• Using the BINARY operator will make INSTR work as the case-sensitive function.

Q-6. Write an SQL query to print the FIRST_NAME from the Worker table after removing white spaces from the right side.

Ans.

The required query is:

Select RTRIM(FIRST_NAME) from Worker;

Q-7. Write an SQL query to print the DEPARTMENT from the Worker table after removing white spaces from the left side.

Ans.

The required query is:

Select LTRIM(DEPARTMENT) from Worker;

Q-8. Write an SQL query that fetches the unique values of DEPARTMENT from the Worker table and prints its length.

Ans.

The required query is:

Select distinct length(DEPARTMENT) from Worker;

Q-9. Write an SQL query to print the FIRST_NAME from the Worker table after replacing ‘a’ with ‘A’.

Ans.

The required query is:

Select REPLACE(FIRST_NAME,'a','A') from Worker;

Q-10. Write an SQL query to print the FIRST_NAME and LAST_NAME from the Worker table into a single column COMPLETE_NAME. A space char should separate them.

Ans.

The required query is:

Select CONCAT(FIRST_NAME, ' ', LAST_NAME) AS 'COMPLETE_NAME' from Worker;

Q-11. Write an SQL query to print all Worker details from the Worker table order by FIRST_NAME Ascending.

Ans.

The required query is:

Select * from Worker order by FIRST_NAME asc;

Q-12. Write an SQL query to print all Worker details from the Worker table order by FIRST_NAME Ascending and DEPARTMENT Descending.

Ans.

The required query is:

Select * from Worker order by FIRST_NAME asc,DEPARTMENT desc;

Q-13. Write an SQL query to print details for Workers with the first names “Vipul” and “Satish” from the Worker table.

Ans.

The required query is:

Select * from Worker where FIRST_NAME in ('Vipul','Satish');

Q-14. Write an SQL query to print details of workers excluding first names, “Vipul” and “Satish” from the Worker table.

Ans.

The required query is:

Select * from Worker where FIRST_NAME not in ('Vipul','Satish');

Q-15. Write an SQL query to print details of Workers with DEPARTMENT name as “Admin”.

Ans.

The required query is:

Select * from Worker where DEPARTMENT like 'Admin%';

Q-16. Write an SQL query to print details of the Workers whose FIRST_NAME contains ‘a’.

Ans.

The required query is:

Select * from Worker where FIRST_NAME like '%a%';

Q-17. Write an SQL query to print details of the Workers whose FIRST_NAME ends with ‘a’.

Ans.

The required query is:

Select * from Worker where FIRST_NAME like '%a';

Q-18. Write an SQL query to print details of the Workers whose FIRST_NAME ends with ‘h’ and contains six alphabets.

Ans.

The required query is:

Select * from Worker where FIRST_NAME like '_____h';

Q-19. Write an SQL query to print details of the Workers whose SALARY lies between 100000 and 500000.

Ans.

The required query is:

Select * from Worker where SALARY between 100000 and 500000;

Q-20. Write an SQL query to print details of the Workers who joined in Feb 2021.

Ans.

The required query is:

Select * from Worker where year(JOINING_DATE) = 2021 and month(JOINING_DATE) = 2;

12 Medium SQL Query Interview Questions / Answers for Practice

At this point, you have acquired a good understanding of the basics of SQL, let’s move on to some more intermediate-level SQL query interview questions. These questions will require us to use more advanced SQL syntax and concepts, such as GROUP BY, HAVING, and ORDER BY.

Q-21. Write an SQL query to fetch the count of employees working in the department ‘Admin’.

Ans.

The required query is:

SELECT COUNT(*) FROM worker WHERE DEPARTMENT = 'Admin';

Q-22. Write an SQL query to fetch worker names with salaries >= 50000 and <= 100000.

Ans.

The required query is:

SELECT CONCAT(FIRST_NAME, ' ', LAST_NAME) As Worker_Name, Salary
FROM worker 
WHERE WORKER_ID IN 
(SELECT WORKER_ID FROM worker 
WHERE Salary BETWEEN 50000 AND 100000);

Q-23. Write an SQL query to fetch the number of workers for each department in descending order.

Ans.

The required query is:

SELECT DEPARTMENT, count(WORKER_ID) No_Of_Workers 
FROM worker 
GROUP BY DEPARTMENT 
ORDER BY No_Of_Workers DESC;

Q-24. Write an SQL query to print details of the Workers who are also Managers.

Ans.

The required query is:

SELECT DISTINCT W.FIRST_NAME, T.WORKER_TITLE
FROM Worker W
INNER JOIN Title T
ON W.WORKER_ID = T.WORKER_REF_ID
AND T.WORKER_TITLE in ('Manager');

Q-25. Write an SQL query to fetch duplicate records having matching data in some fields of a table.

Ans.

The required query is:

SELECT WORKER_TITLE, AFFECTED_FROM, COUNT(*)
FROM Title
GROUP BY WORKER_TITLE, AFFECTED_FROM
HAVING COUNT(*) > 1;

Q-26. Write an SQL query to show only odd rows from a table.

Ans.

The required query is:

SELECT * FROM Worker WHERE MOD (WORKER_ID, 2) <> 0;

Q-27. Write an SQL query to show only even rows from a table.

Ans.

The required query is:

SELECT * FROM Worker WHERE MOD (WORKER_ID, 2) = 0;

Q-28. Write an SQL query to clone a new table from another table.

Ans.

The general query to clone a table with data is:

SELECT * INTO WorkerClone FROM Worker;

The general way to clone a table without information is:

SELECT * INTO WorkerClone FROM Worker WHERE 1 = 0;

An alternate way to clone a table (for MySQL) without data is:

CREATE TABLE WorkerClone LIKE Worker;

Q-29. Write an SQL query to fetch intersecting records of two tables.

Ans.

The required query is:

(SELECT * FROM Worker)
INTERSECT
(SELECT * FROM WorkerClone);

Q-30. Write an SQL query to show records from one table that another table does not have.

Ans.

The required query is:

SELECT * FROM Worker
MINUS
SELECT * FROM Title;

Q-31. Write an SQL query to show the current date and time.

Ans.

The following MySQL query returns the current date:

SELECT CURDATE();

Whereas the following MySQL query returns the current date and time:

SELECT NOW();

Here is a SQL Server query that returns the current date and time:

SELECT getdate();

Find this Oracle query that also returns the current date and time:

SELECT SYSDATE FROM DUAL;

Q-32. Write an SQL query to show the top n (say 10) records of a table.

Ans.

MySQL query to return the top n records using the LIMIT method:

SELECT * FROM Worker ORDER BY Salary DESC LIMIT 10;

SQL Server query to return the top n records using the TOP command:

SELECT TOP 10 * FROM Worker ORDER BY Salary DESC;

Oracle query to return the top n records with the help of ROWNUM:

SELECT * FROM (SELECT * FROM Worker ORDER BY Salary DESC)
WHERE ROWNUM <= 10;

18 Complex SQL Queries for Practice

Now, that you have built a solid foundation in intermediate SQL, It’s time to practice with some advanced SQL query questions. These questions involve queries with more complex SQL syntax and concepts, such as nested queries, joins, unions, and intersects.

Q-33. Write an SQL query to determine the nth (say n=5) highest salary from a table.

Ans.

MySQL query to find the nth highest salary:

SELECT Salary FROM Worker ORDER BY Salary DESC LIMIT n-1,1;

SQL Server query to find the nth highest salary:

SELECT TOP 1 Salary
FROM (
 SELECT DISTINCT TOP n Salary
 FROM Worker 
 ORDER BY Salary DESC
 )
ORDER BY Salary ASC;

Q-34. Write an SQL query to determine the 5th highest salary without using the TOP or limit method.

Ans.

The following query is using the correlated subquery to return the 5th highest salary:

SELECT Salary
FROM Worker W1
WHERE 4 = (
 SELECT COUNT( DISTINCT ( W2.Salary ) )
 FROM Worker W2
 WHERE W2.Salary >= W1.Salary
 );

Use the following generic method to find the nth highest salary without using TOP or limit.

SELECT Salary
FROM Worker W1
WHERE n-1 = (
 SELECT COUNT( DISTINCT ( W2.Salary ) )
 FROM Worker W2
 WHERE W2.Salary >= W1.Salary
 );

Q-35. Write an SQL query to fetch the list of employees with the same salary.

Ans.

The required query is:

Select distinct W.WORKER_ID, W.FIRST_NAME, W.Salary 
from Worker W, Worker W1 
where W.Salary = W1.Salary 
and W.WORKER_ID != W1.WORKER_ID;

Q-36. Write an SQL query to show the second-highest salary from a table.

Ans.

The required query is:

Select max(Salary) from Worker 
where Salary not in (Select max(Salary) from Worker);

Q-37. Write an SQL query to show one row twice in the results from a table.

Ans.

The required query is:

select FIRST_NAME, DEPARTMENT from worker W where W.DEPARTMENT='HR' 
union all 
select FIRST_NAME, DEPARTMENT from Worker W1 where W1.DEPARTMENT='HR';

Q-38. Write an SQL query to fetch intersecting records of two tables.

Ans.

The required query is:

(SELECT * FROM Worker)
INTERSECT
(SELECT * FROM WorkerClone);

Q-39. Write an SQL query to fetch the first 50% of records from a table.

Ans.

The required query is:

SELECT *
FROM WORKER
WHERE WORKER_ID <= (SELECT count(WORKER_ID)/2 from Worker);

Practicing SQL query interview questions is a great way to improve your understanding of the language and become more proficient in SQL. In addition to improving your technical skills, practicing SQL query questions can help you advance your career. Many employers seek candidates with strong SQL skills, so demonstrating your proficiency can get you a competitive edge.

Q-40. Write an SQL query to fetch the departments that have less than five people in them.

Ans.

The required query is:

SELECT DEPARTMENT, COUNT(WORKER_ID) as 'Number of Workers' FROM Worker GROUP BY DEPARTMENT HAVING COUNT(WORKER_ID) < 5;

Q-41. Write an SQL query to show all departments along with the number of people in there.

Ans.

The following query returns the expected result:

SELECT DEPARTMENT, COUNT(DEPARTMENT) as 'Number of Workers' FROM Worker GROUP BY DEPARTMENT;

Q-42. Write an SQL query to show the last record from a table.

Ans.

The following query will return the last record from the Worker table:

Select * from Worker where WORKER_ID = (SELECT max(WORKER_ID) from Worker);

Q-43. Write an SQL query to fetch the first row of a table.

Ans.

The required query is:

Select * from Worker where WORKER_ID = (SELECT min(WORKER_ID) from Worker);

Q-44. Write an SQL query to fetch the last five records from a table.

Ans.

The required query is:

SELECT * FROM Worker WHERE WORKER_ID <=5
UNION
SELECT * FROM (SELECT * FROM Worker W order by W.WORKER_ID DESC) AS W1 WHERE W1.WORKER_ID <=5;

Q-45. Write an SQL query to print the names of employees having the highest salary in each department.

Ans.

The required query is:

SELECT t.DEPARTMENT,t.FIRST_NAME,t.Salary from(SELECT max(Salary) as TotalSalary,DEPARTMENT from Worker group by DEPARTMENT) as TempNew 
Inner Join Worker t on TempNew.DEPARTMENT=t.DEPARTMENT 
 and TempNew.TotalSalary=t.Salary;

Q-46. Write an SQL query to fetch three max salaries from a table.

Ans.

The required query is:

SELECT distinct Salary from worker a WHERE 3 >= (SELECT count(distinct Salary) from worker b WHERE a.Salary <= b.Salary) order by a.Salary desc;

Q-47. Write an SQL query to fetch three min salaries from a table.

Ans.

The required query is:

SELECT distinct Salary from worker a WHERE 3 >= (SELECT count(distinct Salary) from worker b WHERE a.Salary >= b.Salary) order by a.Salary desc;

Q-48. Write an SQL query to fetch nth max salaries from a table.

Ans.

The required query is:

SELECT distinct Salary from worker a WHERE n >= (SELECT count(distinct Salary) from worker b WHERE a.Salary <= b.Salary) order by a.Salary desc;

Q-49. Write an SQL query to fetch departments along with the total salaries paid for each of them.

Ans.

The required query is:

 SELECT DEPARTMENT, sum(Salary) from worker group by DEPARTMENT;

Q-50. Write an SQL query to fetch the names of workers who earn the highest salary.

Ans.

The required query is:

SELECT FIRST_NAME, SALARY from Worker WHERE SALARY=(SELECT max(SALARY) from Worker);

Summary

We hope you enjoyed solving the SQL exercises and learned something new. Stay tuned for our next post, where we’ll bring you even more challenging SQL query interview questions to sharpen your proficiency.

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Enjoy Learning SQL,
Team TechBeamers.