Trigger is a special kind of Store procedure Modifications to the table are made using INSERT,UPDATE OR DELETE trigger will run

It is automatically run

Triggers prevent incorrect , unauthorized, or inconsistent changes to data.

Syntax in Trigger:

CREATE TRIGGER trigger_name ON table_name
FOR [INSERT/UPDATE/DELETE] AS
IF UPDATE(column_name)
{AND/OR} UPDATE(COLUMN_NAME)...]
{ sql_statements }

Trigger Rules:

• A table can have only three triggers action per table : UPDATE ,INSERT,DELETE.
• Only table owners can create and drop triggers for the table.This permission cannot be transferred.
• A trigger cannot be created on a view or a temporary table but triggers can reference them.
• They can be used to help ensure the relational integrity of database.On dropping a table all triggers associated to the triggers are automatically dropped .

INSERT TRIGGER

• When an INSERT trigger statement is executed ,new rows are added to the trigger table and to the inserted table at the same time. 
• The inserted table allows to compare the INSERTED rows in the table to the rows in the inserted table.

DELETE TRIGGER

When a DELETE trigger statement is executed ,rows are deleted from the table and are placed in a special table called deleted table.

UPDATE TRIGGER

When an UPDATE statement is executed on a table that has an UPDATE trigger,

CREATE TABLE statement, as you can see in the following example:
DECLARE @Student TABLE
{
SNO INT ,SNAME NVARCAHR
}

IF YOU WANT INSERT RECORD
INSERT INTO @ Student VALUES(2,’JSSUTHHAAR’)
OR
INSERT INTO @Student SELECT SNO,SNAME FROM STUDENT

SELECT *FROM INFORMATION_SCHEMA.TABLESWHERE
Or
SELECT [name]FROM sys.tables;
table_type = 'BASE TABLE'

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

14. Three tables – student , course, marks – how do go @ 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))

15. 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

16. 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

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

SELECT COUNT(*) AS Counter
FROM syscolumns

WHERE (name = 'empno')

18. 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)

19. 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

20. 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

21. 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

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

SELECT UPPER('test')

23. 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)

24. 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

25. 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 a.col1
FROM a, b
WHERE a.col1 <>
(SELECT b.col1
FROM a, b
WHERE a.col1 = b.col1)
UNION
SELECT b.col1
FROM a, b
WHERE b.col1 <>
(SELECT a.col1
FROM a, b
WHERE a.col1 = b.col1)

26. There are 3 tables Titles, Authors and Title-Authors. 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.

27.

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)
ENDSELECT 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)))

10. 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 *
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: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 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 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 employe 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 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.

Emp City,Empid Empid,empName City,Salary

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

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