Basic SQL Query that Frequently asked in Interview Questions

Introduction:
In this article, I am giving some examples of SQL queries which is frequently asked when you go for a programming interview, having one or two year experience on this field.

These queries test your SQL skill on Joins, both INNER and OUTER join, filtering records by using WHERE and HAVING clause, grouping records using GROUP BY clause, calculating sum, average and counting records using aggregate function like AVG(), SUM() and COUNT(), searching records using wildcards in LIKE operator, searching records in a bound using BETWEEN and IN clause, DATE and TIME queries etc. If you have faced any interesting SQL query or you have any problem and searching for the solution, you can post it here for everyone's benefit.

SQL Query Interview Questions and Answers

Question 1: SQL Query to find second highest salary of Employee
Answer: There are many ways to find second highest salary of Employee in SQL, you can either use SQL Join or Subquery to solve this problem. Here is SQL query using Subquery:

select MAX(Salary) from Employee WHERE Salary NOT IN (select MAX(Salary) from Emp

Question 2: SQL Query to find Max Salary from each department.
Answer: You can find the maximum salary for each department by grouping all records by DeptId and then using MAX() function to calculate maximum salary in each group or each department.

SELECT DeptID, MAX(Salary) FROM Employee  GROUP BY DeptID.

These questions become more interesting if Interviewer will ask you to print department name instead of department id, in that case, you need to join Employee table with Department using foreign key DeptID, make sure you do LEFT or RIGHT OUTER JOIN to include departments without any employee as well.  Here is the query

SELECT DeptName, MAX(Salary) FROM Employee e 
RIGHT JOIN Department d ON e.DeptId = d.DeptID GROUP BY DeptName;

In this query, we have used RIGHT OUTER JOIN because we need the name of the department from Department table which is on the right side of JOIN clause, even if there is no reference of dept_id on Employee table.

Question 3: Write SQL Query to display the current date.
Answer: SQL has built-in function called GetDate() which returns the current timestamp. This will work in Microsoft SQL Server, other vendors like Oracle and MySQL also has equivalent functions.

SELECT GetDate();

Question 4: Write an SQL Query to check whether date passed to Query is the date of given format or not.
Answer: SQL has IsDate() function which is used to check passed value is a date or not of specified format, it returns 1(true) or 0(false) accordingly. Remember ISDATE() is an MSSQL function and it may not work on Oracle, MySQL or any other database but there would be something similar.

SELECT  ISDATE('1/08/13') AS "MM/DD/YY"; 

It will return 0 because passed date is not in correct format. 

Question 5: Write an SQL Query to print the name of the distinct employee whose DOB is between 01/01/1960 to 31/12/1975.
Answer: This SQL query is tricky, but you can use BETWEEN clause to get all records whose date fall between two dates.

SELECT DISTINCT EmpName FROM Employees 
WHERE DOB  BETWEEN ‘01/01/1960’ AND ‘31/12/1975’;

Question 6: Write an SQL Query find number of employees according to gender  whose DOB is between 01/01/1960 to 31/12/1975.
Answer :

SELECT COUNT(*), sex from Employees  
WHERE  DOB BETWEEN '01/01/1960' AND '31/12/1975' GROUP BY sex;

Question 7: Write an SQL Query to find an employee whose Salary is equal or greater than 10000.
Answer :

SELECT EmpName FROM  Employees WHERE  Salary>=10000;

Question 8: Write an SQL Query to find name of employee whose name Start with ‘M’
Answer :

SELECT * FROM Employees WHERE EmpName like 'M%';

Question 9: find all Employee records containing the word "Joe", regardless of whether it was stored as JOE, Joe, or joe.
Answer :

SELECT * from Employees  WHERE  UPPER(EmpName) like '%JOE%';

Question 10: Write an SQL Query to find  the year from date.
Answer:  Here is how you can find Year from a Date in SQL Server 2008

SELECT YEAR(GETDATE()) as "Year";