Top 51 SQL Query Interview Questions and Answers

Introduction

Are you preparing for an SQL interview? But confused what are the primary SQL Query Interview Questions you may be asked? 

Well, here is the solution!

We have listed here the Top 51 SQL Query Interview Questions and Answers to help you understand the depth and real-intend of SQL-related questions asked.

Are you looking to break into the world of database administration? Do you want to know if this career path is right for you? Keeping up with database technologies can be challenging, but it can also present great opportunities for growth and professional development. If you’re looking for a job as a database administrator, or want to make DB administration your primary field, you need to ace your next SQL interview. 

Data Structures and Query Language (commonly known as SQL) is the standard language that almost every relational database management system uses. An in-depth understanding of the principles behind relational databases will increase your chances of success in any SQL interview. Even if you are not sure whether you want to pursue a career in this field, an awareness of these concepts will help you get ahead in any job search.  To become a top leading SQL professional, come and join our SQL Training & Certification Program.

The below list covers all the SQL Query Interview Questions for experienced candidates and some SQL technical interview questions on the advanced level.

Check the basic SQL Interview questions to begin your journey before going on the tricky SQL queries.
So without any further ado, let’s get started.

Top 51 SQL Query Interview Questions and Answers, You shouldn’t Miss

Here are the  SQL Query Interview Question often asked individuals applying for the senior-level positions.

1. What is a Query?

A query is basically a request for data from a database table. It can be either a select query or an action query.

SELECT fname, lname    /* select query */
FROM myDb.students
WHERE student_id = 1;
UPDATE myDB.students    /* action query */ 
 SET fname = 'Captain', lname = 'America' 
 WHERE student_id = 1; 

This is an important answer to these kinds of SQL Queries interview questions

2. What is a Subquery? What are its types?

A query within another query is called a subquery. It is mainly used to either restrict or make the data better that to be queried by the main query, hence restricting or making the output of the main query better. 

There are two types of subquery - Correlated and Non-Correlated.

Correlated subquery: It is not considered as an independent query, but can refer to the column in a table listed in the FROM of the main query.

Non-correlated subquery: Considered as an independent query, the output of the non-correlated subquery is substituted in the main query.

It one of the most important SQL interview queries one needs to be preareped  for. 

Our Data Management Certification Courses for Freshers and Advanced Professionals assure to upskill your SQL and RDBMS fundamentals that enhances your career prospects. 

3. What are the types of SQL Queries?

There are five types of SQL queries: 

• Data Definition Language (DDL) 
• Data Manipulation Language (DML) 
• Data Control Language(DCL) 
• Transaction Control Language(TCL) 
• Data Query Language (DQL) Data Definition Language(DDL).

These different types of SQL queries help you define the database structure or schema. This is a critical response to these types of SQL Query interview questions.

Gain a credible certified by enrolling with Janbask Training. Get hands-on experience with real world projects and get trained from top industry professionals.

4. What is the SQL query to display the current date?

SQL Server GETDATE() Function

To get the current date in SQL Server, use the GETDATE() function.

This is another one of the widespread SQL Queries Interview Questions in which the interviewer wants to check the knowledge of SQL professionals. 

5. Write a query to access the first record from the SQL table?

Here is Syntax to get the first record from the table:

SELECT * FROM Table_Name WHERE Rownum = 1;  

The first row of any table can be easily accessed by assigning 1 to the Rownum keyword in the WHERE clause of the SELECT statement.

It is a good response to these kinds of MySQL query interview questions. 

6. Write an SQL query to remove duplicates from a table without using a temporary table.

Here, the delete option can be used with alias and inner join. First, go through the equality of all the matching records and then remove the row with higher EmpId.

DELETE E1 FROM EmployeeDetails E1 

 INNER JOIN EmployeeDetails E2  

 WHERE E1.EmpId > E2.EmpId  

 AND E1.FullName = E2.FullName  

 AND E1.ManagerId = E2.ManagerId 

 AND E1.DateOfJoining = E2.DateOfJoining 

 AND E1.City = E2.City;

This is a key response to these types of SQL Query interview questions.

Join the Janbask Training SQL community for better networking and knowledge.

7. Write a query in SQL to find the minimum and maximum number from the integer column.

The MIN() function returns the smallest value of the selected column. The MAX() function returns the largest value of the selected column.

This is an important answer to these kinds of SQL Queries interview questions.

8. Write a query to create a View in Structured Query Language.

CREATE VIEW View_Name AS SELECT Column_Name1, Column_Name2, ..... FROM Table_Name WHERE Condition;  

For Creating a View in SQL, we have to use the Create View statement with the SELECT statement.   

This is another one of the very common SQL Queries Interview Questions in which the interviewer wants to check the knowledge of SQL professionals.

9. Write a query to retrieve the top N records.

By using the TOP command in SQL Server:

SELECT TOP N * FROM EmployeePosition ORDER BY Salary DESC; 

By using the LIMIT command in MySQL:

SELECT * FROM EmpPosition ORDER BY Salary DESC LIMIT N;

This is a key response to these types of SQL Query interview questions.

If you want to learn the concepts of DataStage to ace your upcoming interview, read our blog on top 50 DataStage Interview Questions and Answers.

10. Create a query to generate the first and last records from the EmployeeInfo table.

To generate the first record from the EmployeeInfo table, you need to write a query as follows:

SELECT * FROM EmployeeInfo WHERE EmpID = (SELECT MIN(EmpID) FROM EmployeeInfo);

To generate the last record from the EmployeeInfo table, you need to write a query as follows:

SELECT * FROM EmployeeInfo WHERE EmpID = (SELECT MAX(EmpID) FROM EmployeeInfo);

It is one of the basic SQL queries interview questions that can be asked. 

11. Write a query to find duplicate records from a table.

To Find Duplicate Records in the table, use the following query:

select a.* from Employee a where rowid != 

         (select max(rowid) from Employee b where  a.Employee_num =b.Employee_num;

This is a key response to these types of SQL Query interview questions.

12. What is query to retrieve the last 3 records from the EmployeeInfo table.

To retrieve the last 3 records, write the follow query:

SELECT * FROM EmployeeInfo WHERE 

 EmpID <=3 UNION SELECT * FROM 

 (SELECT * FROM EmployeeInfo E ORDER BY E.EmpID DESC)  

 AS E1 WHERE E1.EmpID <=3;

It one of the most important SQL interview queries one needs to be preareped  for. 

If you are learning SQL and want to improve your SQL language then you should start practicing SQL right away.  Read our blog on Top Practice Questions On SQL Queries.

13. Write a query to view the specific record of the table by using the WHERE clause.

To view specific records from the table, here is the query to follow:

SELECT * FROM Table_Name WHERE condition;

This is an important answer to these kinds of SQL query interview questions. 

14. Write a query to fetch the EmpFname from the EmployeeInfo table in the upper case and use the ALIAS name as EmpName.

Syntax to fetch the EmpFname from the EmployeeInfo table in the upper case:

SELECT UPPER(EmpFname) AS EmpName FROM EmployeeInfo;

It one of the most important SQL interview queries one needs to be preareped  for. 

15. Write a query to fetch the number of employees working in the department ‘HR’.

Here is the query to fetch the number of employees :

SELECT COUNT(*) FROM EmployeeInfo WHERE Department = 'HR';

This is a key response to these types of SQL Query interview questions. 

16. Write a query to get the current date.

To get the current date, you need write a query as follows in SQL Server:

SELECT GETDATE(); 

Write a query as follows in MySQL:

SELECT SYSTDATE();

It is one of the basic SQL queries interview questions that can be asked. 

Looking to ace your SQL skill-sets, join Janbask Training now!

17. Write a query in SQL to find the second-highest value of an integer column from the table?

Here is the Syntax to find the second highest value of the integer column:

Select MAX(Column_Name) from Table_Name    

 where Column_Name NOT IN (Select MAX(Column_Name) from Table_Name); 

This is a key response to these types of SQL Query interview questions.

18. Write a query to transform any value into the specific SQL data type.

Here is the query to convert the floating-point value into the integer type.

SELECT CONVERT (int, 3025.58);  ‘

This is an important answer to these kinds of SQL Queries interview questions 

19. Write a query to retrieve the first four characters of  EmpLname from the EmployeeInfo table.

SELECT SUBSTRING(EmpLname, 1, 4) FROM EmployeeInfo;

This is a key response to these types of SQL Query interview questions. 

20. Write a query to fetch only the place name(string before brackets) from the Address column of EmployeeInfo table.

By using the MID function in MySQL:

SELECT MID(Address, 0, LOCATE('(',Address)) FROM EmployeeInfo;

By using SUBSTRING:

SELECT SUBSTRING(Address, 1, CHARINDEX('(',Address)) FROM EmployeeInfo;

This is an important answer to these kinds of SQL query interview question.

21. Write a query to create a new table that consists of data and structure copied from the other table.

Here are the queries to follow:

By using the SELECT INTO command:

SELECT * INTO NewTable FROM EmployeeInfo WHERE 1 = 0;

By using the CREATE command in MySQL:

CREATE TABLE NewTable AS SELECT * FROM EmployeeInfo;

It is one of the basic SQL queries interview questions that can be asked. 

22. Write an SQL query to fetch intersecting records of two tables.

The required query to fetch intersecting records of two tables:

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

This is a Key response to these types of SQL Query interview questions. 

23. Write q query to find all the employees whose salary is between 50000 to 100000.

Here is the required query:

SELECT * FROM EmployeePosition WHERE Salary BETWEEN '50000' AND '100000';

This is a key response to these types of SQL Query interview questions.

24. Write a query to find the names of employees that begin with ‘S’

The required query to find the names:

SELECT * FROM EmployeeInfo WHERE EmpFname LIKE 'S%';

It is one of the basic SQL queries interview questions that can be asked. 

Do you know the best way to become an SQL Developer? Read our blog to learn more about job duties, roles and responsibilities and Skills required to be an SQL Developer.

25. Write a query to fetch top N records.

This is an important answer to these kinds of SQL query interview question. There are two ways to fetch top N records. First, by using the TOP command in SQL Server:

SELECT TOP N * FROM EmployeePosition ORDER BY Salary DESC;

Second, through the LIMIT command in MySQL:

SELECT * FROM EmpPosition ORDER BY Salary DESC LIMIT N;

This is a key response to these types of SQL Query interview questions.

If you want to Test Your SQL Skills, Play our online SQL Quiz and find out where you stand!

26. Write an SQL query to fetch only even rows from the table.

If you have an auto-increment field e.g. EmpId then you can easily follow the below query to fetch even row-

SELECT * FROM EmployeeDetails  

 WHERE MOD (EmpId, 2) = 0;

If you don’t have such a field then you need to use the below queries.

Using Row_number in SQL server and checking that the remainder when divided by 2 is 1-

SELECT E.EmpId, E.Project, E.Salary 

 FROM ( 

     SELECT *, Row_Number() OVER(ORDER BY EmpId) AS RowNumber 

     FROM EmployeeSalary 

 ) E 

 WHERE E.RowNumber % 2 = 0; 

You can also use a user defined variable in MySQL-

SELECT * 

 FROM ( 

       SELECT *, @rowNumber := @rowNumber+ 1 rn 
       FROM EmployeeSalary 

       JOIN (SELECT @rowNumber:= 0) r 

      ) t  

 WHERE rn % 2 = 0;

This is a key response to these types of SQL Query interview questions.

27. Write an SQL query to fetch only odd rows from the table.

If you have an auto-increment field e.g. EmpId then you can easily use the below query-

SELECT * FROM EmployeeDetails  

WHERE MOD (EmpId, 2) <> 0;

If you  don’t have such a field then you need to use the below queries.

Using Row_number in SQL server and checking that the remainder when divided by 2 is 1-

SELECT E.EmpId, E.Project, E.Salary 

 FROM ( 

     SELECT *, Row_Number() OVER(ORDER BY EmpId) AS RowNumber 

     FROM EmployeeSalary 

 ) E 

 WHERE E.RowNumber % 2 = 1; 

You can also use a user defined variable in MySQL-

SELECT * 

FROM ( 

       SELECT *, @rowNumber := @rowNumber+ 1 rn 

       FROM EmployeeSalary 

       JOIN (SELECT @rowNumber:= 0) r 

      ) t  

WHERE rn % 2 = 1;

It is one of the basic SQL queries interview questions that can be asked. 

 

Looking to take online SQL training? It's never too late to build your SQL Career Path, changing your life and bringing you satisfaction. 

28. Write a query to retrieve the EmpFname and EmpLname in a single column as “FullName”. The first name and the last name must be separated with space.

Need to follow the below query:

SELECT CONCAT(EmpFname, ' ', EmpLname) AS 'FullName' FROM EmployeeInfo;

This is an important answer to these kinds of SQL query interview questions.

29. SQL Query to fetch records that are present in one table but not in another table.

SQL Server – Using MINUS- operator-

SELECT * FROM EmployeeSalary 

 MINUS 

 SELECT * FROM ManagerSalary; 

MySQL – Since MySQL doesn’t have MINUS operator so we can use LEFT join-

SELECT EmployeeSalary.* 

 FROM EmployeeSalary 

 LEFT JOIN 

 ManagerSalary USING (EmpId) 

 WHERE ManagerSalary.EmpId IS NULL; 

This is a Key response to these types of SQL Query interview questions.

30. Write an SQL query to create an empty table with the same structure as some other table.

 Here is the query-

CREATE TABLE NewTable  

 SELECT * FROM EmployeeSalary where 1=0;

This is a Key response to these types of SQL Query interview questions.

31. SQL query to fetch all the employees who are not working on any project.

It is one of the very basic SQL Query Interview Question in which the interviewer wants to check if the person knows about the commonly used – Is NULL operator.

SELECT EmpId  

 FROM EmployeeSalary  

 WHERE Project IS NULL;

It is one of the basic SQL queries interview questions that can be asked. 

32. SQL query to fetch all the Employees from EmployeeDetails who joined in the Year 2020.

To fetch all the employees details, use BETWEEN for the date range ’01-01-2020′ AND ’31-12-2020′-

SELECT * FROM EmployeeDetails 

 WHERE DateOfJoining BETWEEN '2020/01/01' 

 AND '2020/12/31'; 

Also, you can extract year part from the joining date by using YEAR in mySQL-

SELECT * FROM EmployeeDetails  

 WHERE YEAR(DateOfJoining) = '2020';

This is a key response to these types of SQL Query interview questions.

33. Write an SQL query to display the total salary of each employee adding the Salary with Variable value.

Here, you need to simply use the ‘+’ operator in SQL.

SELECT EmpId, 

 Salary+Variable as TotalSalary  

 FROM EmployeeSalary;

This is an important answer to these kinds of SQL Queries interview questions.

34. Write an SQL query to find the maximum, minimum, and average salary of the employees.

To fetch the max, min, and average values,  use the aggregate function of SQL:  

SELECT Max(Salary),  

 Min(Salary),  

 AVG(Salary)  

 FROM EmployeeSalary;

This is a key response to these types of SQL Query interview questions. 

35. Fetch all employees from EmployeeDetails who have a salary record in EmployeeSalary.

You can fetch all employees by using ‘Exists’-

SELECT * FROM EmployeeDetails E 

 WHERE EXISTS 

 (SELECT * FROM EmployeeSalary S  
 WHERE  E.EmpId = S.EmpId);

It one of the most important SQL interview queries one needs to be preareped  for. 

36. Write an SQL query to fetch project-wise count of employees sorted by project’s count in descending order.

The SQL query has two major needs– To fetch the project-wise count and then to sort the result by that count. 

For project-wise count, the GROUP BY clause is used and for sorting, the ORDER BY clause is used on the alias of the project-count.

SELECT Project, count(EmpId) EmpProjectCount 

 FROM EmployeeSalary 

 GROUP BY Project 

 ORDER BY EmpProjectCount DESC;

This is an important answer to these kinds of SQL Queries interview questions 

37. Write an SQL query to fetch duplicate records from EmployeeDetails (without considering the primary key. 

To fetch duplicate records from the table, the GROUP BY is used on all the fields and then the HAVING clause is used to return only those fields whose count is greater than 1 i.e. the rows having duplicate records.

SELECT FullName, ManagerId, DateOfJoining, City, COUNT(*)  

 FROM EmployeeDetails 

 GROUP BY FullName, ManagerId, DateOfJoining, City 

 HAVING COUNT(*) > 1;

This is a key response to these types of SQL Query interview questions.

38. Write a query in SQL to create a new table with the same data and structure as an existing table.

To create a new table, the SQL CREATE TABLE syntax is: 

CREATE TABLE new_table AS (SELECT * FROM old_table WHERE 1=2); For example: CREATE TABLE suppliers AS (SELECT * FROM companies WHERE 1=2);

It is one of the basic SQL queries interview questions that can be asked. 

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

The required query to fetch duplicate records is –

SELECT WORKER_TITLE, AFFECTED_FROM, COUNT(*)

 FROM TitleGROUP BY WORKER_TITLE, AFFECTED_FROMHAVING COUNT(*) > 1;

40. Fetch employee names and salaries even if the salary value is not present.

Here, you can use left join with EmployeeDetail table on the left side of the EmployeeSalary table.

SELECT E.FullName, S.Salary  

 FROM EmployeeDetails E  

 LEFT JOIN  

 EmployeeSalary S 

 ON E.EmpId = S.EmpId;

This is another one of the very common SQL Query Interview Questions in which the interviewer wants to check the knowledge of SQL professionals.

41. Write an SQL query to show the last record from a table.

Use the below to show the last record from the Worker table:

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

This is another one of the very common SQL Queries Interview Questions in which the interviewer wants to check the knowledge of SQL professionals.

42. Write an SQL query to fetch all the Employees who are also managers.

 There is Self-Join as the requirement need analyst is the EmployeeDetails table as two tables. Here, two different aliases ‘E’ and ‘M’ for the same EmployeeDetails table.

SELECT DISTINCT E.FullName 

 FROM EmployeeDetails E 

 INNER JOIN EmployeeDetails M 

 ON E.EmpID = M.ManagerID;

This is a Key response to these types of SQL Query interview questions. 

43. Write an SQL query to fetch duplicate records from EmployeeDetails.

To fetch duplicate records from the table, the GROUP BY is used on all the fields and then the HAVING clause is used to return only those fields whose count is greater than 1 i.e. the rows having duplicate records.

SELECT FullName, ManagerId, DateOfJoining, City, COUNT(*) 

 FROM EmployeeDetails 

 GROUP BY FullName, ManagerId, DateOfJoining, City 

 HAVING COUNT(*) > 1; 

This is another one of the prevalent SQL Query Interview Questions in which the interviewer wants to check the knowledge of SQL professionals.

44. What are the differences between SQL and PL/SQL?

Here are the differences between SQL and PL/SQL: 

SQL is a structured query language for databases. This query executes a single operation at a time

Pl/SQL: A procedural language designed to implement SQL statements. And, here, the Group of operations is performed in a single block.

This is another one of the very common SQL Queries Interview Questions in which the interviewer wants to check the knowledge of SQL professionals.

45. What is the difference between SQL and MySQL?

SQL is a programming language used for database systems, while MySQL is used in all the primary programming languages like C, C++, Perl, PHP, Python, Ruby, and more.

It is one of the basic SQL queries interview questions that can be asked. 

46. Name different types of case manipulation functions available in SQL.

Here are two different types of case manipulation:

LOWER. The lower function converts a given string into a lower case. 

UPPER: The upper Function converts the given character String to Upper Case.

It is a good response to these kinds of MySQL query interview questions. 

47. What is the difference between primary key and unique constraints?

You can create multiple UNIQUE constraints in a table, while in the PRIMARY KEY, you can create only one SQL per table. 

UNIQUE constraint allows for one NULL value, but the PRIMARY KEY does not allow NULL values.

This is another one of the very common SQL Query Interview Questions  in which the interviewer wants to check the knowledge of SQL professionals.

48. What is the difference between a primary key and a unique key?

While both keys provide a guaranteed uniqueness for a column or a set of columns in a table or relation, the difference is that the primary key identifies each record in the table, and the unique key prevents duplicate entries in a column except for a NULL value.

This is another one of the very common SQL Queries Interview Questions in which the interviewer wants to check the knowledge of SQL professionals.

49. What are functions and their usage in SQL?

A function is a set of SQL statements used to do a specific task. The main use of functions is to foster code reusability. When you are repeatedly writing large SQL scripts to do the same task, you can create a function to do that task. So, next time you do not need of rewrite the SQL, you can simply call that function.

It is one of the basic SQL queries interview questions that can be asked. 

50. How many Aggregate functions are available in SQL?

There are five aggregate functions in SQL –  MIN, MAX, COUNT, SUM, and AVG.

This is another one of the very common SQL Query Interview Question s in which the interviewer wants to check the knowledge of SQL professionals.

51. What are all the different attributes of indexes?

There are mainly three attributes of indexing: Clustered Indexing. Non-Clustered, and Multilevel Indexing.

It is one of the most important SQL interview queries one needs to be prepared  for. 

Last Verdicts on SQL Query Interview Questions

These are the most popular and useful SQL interview questions and answers. These MySQL query interview questions are created specifically to familiarise you with the types of questions you might encounter during your SQL interview. If you are just starting out and need a professional guide, go for the SQL Server Training & Certification course.  Here are a few frequently asked questions related to the SQL career. 

Frequently Asked Questions

How does training help in cracking the SQL job interview?

SQL server training helps to build good SQL queries helps develop team members’ logical thinking skills. And optimizing SQL queries helps you know which questions you will be asked, and how those questions should best be phrased.

What is the correct SQL career path?

SQL career path includes SQL Server Database Administration and Development, Business intelligence professionals, Data science, and engineering will come in successful SQL career path.

How to become a SQL professional?

Here is a step-wise process to become an SQL professional: 

1. Complete a bachelor's degree
2. Find an internship
3. Improve your database knowledge
4. Gain hands-on experience
5. Get certified to become certified SQL professional
6. Improve your soft skills

What is the SQL developer's salary? 

The average SQL developer salary is $87,125 per year in the United States and $5,000 cash bonus per year. For more details over salary check out detailed insights on SQL developer salary.

Thanks for checking this post so far. If you like these SQL interview questions, then please share this post with your friends and colleagues. If you have any questions or feedback, feel free to let us know in the comment below

FaceBook Twitter Google+ LinkedIn Pinterest Email