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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.
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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.
Here are the SQL Query Interview Question often asked individuals applying for the senior-level positions.
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
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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.
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There are five types of SQL queries:
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.
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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.
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.
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.
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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.
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.
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
EmpPositionORDER BY
SalaryDESC LIMIT N;
This is a key response to these types of SQL Query interview questions.
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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.
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.
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.
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.
Syntax to fetch the EmpFname from the EmployeeInfo table in the upper case:
SELECT UPPER
(EmpFname) AS EmpNameFROM
EmployeeInfo;
It one of the most important SQL interview queries one needs to be preareped for.
Here is the query to fetch the number of employees :
SELECT COUNT(*) FROM
EmployeeInfoWHERE
Department ='HR';
This is a key response to these types of SQL Query interview questions.
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.
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Here is the Syntax to find the second highest value of the integer column:
SelectMAX(Column_Name) from Table_Name
whereColumn_Name NOT IN (Select MAX(Column_Name) from Table_Name);
This is a key response to these types of SQL Query interview questions.
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.
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.
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.
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.
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.
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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.
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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.
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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.
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.
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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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
The required query to fetch duplicate records is –
SELECT WORKER_TITLE, AFFECTED_FROM, COUNT(*)
FROM Title
GROUP BY WORKER_TITLE, AFFECTED_FROM
HAVING COUNT(*) > 1;
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.
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.
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.
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.
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.
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.
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.
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 oneNULL
value, but thePRIMARY KEY
does not allowNULL
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.
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.
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.
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.
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.
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.
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:
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.
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Dizzy
I found your blog today and it is very well written. Keep up the good work & share more about SQL Interview Questions.
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Sure, we will soon come up with a new guidepost on the SQL interview preparation.
Kaden Brown
Such an interesting post! Very well explained, very understanding with so many SQL Query Interview Questions.
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That’s interesting to hear from you! Keep coming back to our website to read more content.
Paul Wilson
Thanks for sharing so many SQL Query Interview Questions. A lot of people want to know more about this and its benefits. so I’m really happy that I got to find your site before using it.
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It’s our pleasure that we could help you. Feel free to write to us if you have any questions.
Louis Anderson
Such an informative and great article! Every beginner or experienced in SQL must read this article. This is very helpful for me and people who want to become a SQL professional.
JanbaskTraining
Glad to hear that you found this post helpful! Often visit our site for more interesting content.
Caden Thomas
Really good article on SQL Query Interview Question. I got all my confusions clear about this particular topic after reading this blog. Thanks for sharing this blog.
JanbaskTraining
Glad to hear that you found this post helpful! Often visit our site for more interesting content.
Holden White
Hey, Thanks for this Great Article, for sharing content and such nice information for me. I hope you will share some more content about it. Please keep sharing!
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That’s great! Let us know if you have any more questions.
Rock
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Sure, we will keep posting such content. Often visit our site for such valuable insights.
John
Great stuff! I’m looking to become an SQL professional. Thank you so much for sharing! It’s a pleasure to hear from you that you found the blog a valuable read.
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Surely, we will try to come up with more blog posts.
Paxton Harris
Wow! After going through the whole post I must say it is superb. I was actively looking for such a great guide on cracking the next SQL interview. Thanks.
JanbaskTraining
Glad to hear from you, thanks for your valuable review.
Bryan Garcia
Awesome blog! I have learned so much about the SQL Query Interview, most frequently asked questions, important query related questions, etc.
JanbaskTraining
You are always welcome! Keep coming back to our site for such more valuable insights.