T-SQL Queries Interview Questions

1. 2 tables
Employee
empid
empname
salary
mgrid

Phone
empid
phnumber

2. Select all employees who doesn't have phone?

SELECT empname FROM Employee
WHERE (empid NOT IN (SELECT DISTINCT empid FROM phone))

3. Select the employee names who is having more than one phone numbers.

SELECT empname FROM employee
WHERE (empid IN (SELECT empid FROM phone GROUP BY empid HAVING COUNT(empid) > 1))

4. Select the details of 3 max salaried employees from employee table.

SELECT TOP 3 empid, salary FROM employee
ORDER BY salary DESC

5. Display all managers from the table. (manager id is same as emp id)

SELECT empname FROM employee
WHERE (empid IN (SELECT DISTINCT mgrid FROM employee))

6. Write a Select statement to list the Employee Name, Manager Name under a particular manager?

SELECT e1.empname AS EmpName, e2.empname AS ManagerName
FROM Employee e1 INNER JOIN Employee e2
ON e1.mgrid = e2.empid
ORDER BY e2.mgrid

7. 2 tables emp and phone.
emp fields are - empid, name
Ph fields are - empid, ph (office, mobile, home). Select all employees who doesn't have any ph nos.

SELECT * FROM employee
LEFT OUTER JOIN phone
ON employee.empid = phone.empid
WHERE (phone.office IS NULL OR phone.office = ' ')
AND (phone.mobile IS NULL OR phone.mobile = ' ')
AND (phone.home IS NULL OR phone.home = ' ')

8. Find employee who is living in more than one city.
Two Tables:
employee
Emp
Empid
empName
Salary

City
Empid
City

9.
SELECT empname, fname, lname
FROM employee
WHERE (empid IN (SELECT empid FROM city GROUP BY empid HAVING COUNT(empid) > 1))

10. Find all employees who is living in the same city. (table is same as above)

SELECT fname FROM employee
WHERE (empid IN (SELECT empid FROM city a WHERE city IN (SELECT city FROM city b GROUP BY city
HAVING COUNT(city) > 1)))

11. There is a table named MovieTable with three columns - moviename,
person and role. Write a query which gets the movie details where Mr.
Amitabh and Mr. Vinod acted and their role is actor.

SELECT DISTINCT m1.moviename FROM MovieTable m1
INNER JOIN MovieTable m2
ON m1.moviename = m2.moviename
WHERE (m1.person = 'amitabh' AND m2.person = 'vinod' OR m2.person = 'amitabh' AND m1.person = 'vinod') AND (m1.role = 'actor') AND (m2.role = 'actor')
ORDER BY m1.moviename

12. There are two employee tables named emp1 and emp2. Both contains
same structure (salary details). But Emp2 salary details are incorrect
and emp1 salary details are correct. So, write a query which corrects
salary details of the table emp2

update a set a.sal=b.sal from emp1 a, emp2 b where a.empid=b.empid

13.Given a Table named “Students” which contains studentid, subjectid and
marks. Where there are 10 subjects and 50 students. Write a Query to
find out the Maximum marks obtained in each subject.

14.In this same tables now write a SQL Query to get the studentid also to
combine with previous results.

15. Three tables – student , course, marks – how do go at finding name of
the students who got max marks in the diff courses.

SELECT student.name, course.name AS coursename, marks.sid,
marks.mark FROM marks
INNER JOIN student
ON marks.sid = student.sid
INNER JOIN course
ON marks.cid = course.cid WHERE (marks.mark = (SELECT MAX(Mark)FROM Marks MaxMark
WHERE MaxMark.cID = Marks.cID))

16. There is a table day_temp which has three columns dayid, day and
temperature. How do I write a query to get the difference of
temperature among each other for seven days of a week?

SELECT a.dayid, a.dday, a.tempe, a.tempe - b.tempe AS Difference FROM day_temp
a INNER JOIN day_temp b
ON a.dayid = b.dayid + 1

OR

Select a.day, a.degree-b.degree from temperature a, temperature b
where a.id=b.id+1

17. There is a table which contains the names like this. a1, a2, a3, a3, a4, a1, a1, a2 and their salaries. Write a query to get grand total salary, and total salaries of individual employees in one query.

SELECT empid, SUM(salary) AS salary
FROM employee
GROUP BY empid WITH ROLLUP
ORDER BY empid

18. How to know how many tables contains empno as a column in a database?

SELECT COUNT(*) AS Counter
FROM syscolumns
WHERE (name = 'empno')

19. Find duplicate rows in a table? OR I have a table with one column which has many records which are not distinct. I need to find the distinct values from that column and number of times it’s repeated.

SELECT sid, mark, COUNT(*) AS Counter
FROM marks
GROUP BY sid, mark
HAVING (COUNT(*) > 1)

20. How to delete the rows which are duplicate (don’t delete both duplicate records).

SET ROWCOUNT 1
DELETE yourtable FROM yourtable a
WHERE (SELECT COUNT(*) FROM yourtable b WHERE b.name1 = a.name1 AND b.age1 = a.age1) > 1
WHILE @@rowcount > 0

DELETE yourtable FROM yourtable a WHERE (SELECT COUNT(*) FROM yourtable b WHERE b.name1 = a.name1 AND b.age1 = a.age1) > 1
SET ROWCOUNT 0

21. How to find 6th highest salary

SELECT TOP 1 salary FROM (SELECT DISTINCT TOP 6 salary FROM employee ORDER BY salary DESC) a
ORDER BY salary

22. Find top salary among two tables

SELECT TOP 1 sal FROM (SELECT MAX(sal) AS sal FROM sal1
UNION
SELECT MAX(sal) AS sal FROM sal2) a
ORDER BY sal DESC

23. Write a query to convert all the letters in a word to upper case

SELECT UPPER('test')

24. Write a query to round up the values of a number. For example even if the user enters 7.1 it should be rounded up to 8.

SELECT CEILING (7.1)

25. Write a SQL Query to find first day of month?

SELECT DATENAME(dw, DATEADD(dd, - DATEPART(dd, GETDATE()) + 1,GETDATE())) AS FirstDay

Datepart Abbreviations
year yy, yyyy
quarter qq, q
month mm, m
dayofyear dy, y
day dd, d
week wk, ww
weekday dw
hour hh
minute mi, n
second ss, s
millisecond ms

26. Table A contains column1 which is primary key and has 2 values (1, 2) and Table B contains column1 which is primary key and has 2 values (2, 3). Write a query which returns the values that are not common for the tables and the query should return one column with 2 records.

SELECT tbla.a FROM tbla, tblb
WHERE tbla.a <> (SELECT tblb.a FROM tbla, tblb WHERE tbla.a = tblb.a)
UNION
SELECT tblb.a FROM tbla, tblb
WHERE tblb.a <> (SELECT tbla.a FROM tbla, tblb WHERE tbla.a = tblb.a)

OR (better approach)

SELECT a FROM tbla
WHERE a NOT IN (SELECT a FROM tblb)
UNION ALL
SELECT a FROM tblb
WHERE a NOT IN (SELECT a FROM tbla)

27. There are 3 tables Titles, Authors and Title-Authors (check PUBS db).
Write the query to get the author name and the number of books written by that author, the result should start from the author who has written the maximum number of books and end with the author who has written the minimum number of books.

SELECT authors.au_lname, COUNT(*) AS BooksCount FROM authors INNER JOIN
titleauthor ON authors.au_id = titleauthor.au_id INNER JOIN
titles ON titles.title_id = titleauthor.title_id
GROUP BY authors.au_lname
ORDER BY BooksCount DESC

28. UPDATE emp_master
SET emp_sal = CASE WHEN emp_sal > 0 AND emp_sal <= 20000 THEN (emp_sal * 1.01) WHEN emp_sal > 20000 THEN (emp_sal * 1.02)
END

29. List all products with total quantity ordered, if quantity ordered is null show it as 0.

SELECT name, CASE WHEN SUM(qty) IS NULL THEN 0 WHEN SUM(qty) > 0 THEN SUM(qty) END AS tot FROM [order] RIGHT OUTER JOIN product
ON [order].prodid = product.prodid
GROUP BY name

Result:
coke 60
mirinda 0
pepsi 10

30.ANY, SOME, or ALL?
ALL means greater than every value--in other words, greater than the
maximum value. For example, >ALL (1, 2, 3) means greater than 3.
ANY means greater than at least one value, that is, greater than the minimum. So >ANY (1, 2, 3) means greater than 1.
SOME is an SQL-92 standard equivalent for ANY.

31. IN & = (difference in correlated sub query)