Difference between Index Seek vs. Index Scan

What is the Difference between Index Seek vs. Index Scan?

Index Scan:

An index scan means that SQL Server reads all the rows in a table, and then returns only those rows that satisfy the search criteria. When an index scan is performed, all the rows in the leaf level of the index are scanned. This essentially means that all the rows of the index are examined instead of the table directly. This is sometimes compared to a table scan, in which all the table data is read directly.

Index Seek:

 An index seek, on the other hand, means that the Query Optimizer relies entirely on the index leaf data to locate rows satisfying the query condition. An index seek will be most beneficial in cases where a small percentage of rows will be returned. An index seek will only affect the rows that satisfy a query condition and the pages that contain these qualifying rows; in terms of performance, this is highly beneficial when a table has a very large number of rows.

ROW_NUMBER() OVER PARTITION BY IN SQL

ROW_NUMBER()

Returns the sequential number of a row within a partition of a result set, starting at 1 for the first row in each partition.

PARTITION BY value_expression

Divides the result set produced by the FROM clause into partitions to which the ROW_NUMBER function is applied. value_expression specifies the column by which the result set is partitioned. If PARTITION BY is not specified, the function treats all rows of the query result set as a single group.

Select * from Row_Number (table name)

Fname	Salary	State
Vipin	10000	Delhi
Chandra	9000	Delhi
Taslim	8000	UP
Raghu	12000	UP
Ravi	6000	MP
Jatin	7000	MP
Neeraj	16000	AP
Manish	5000	Delhi
Vijay	23000	Delhi

SELECT ROW_NUMBER() OVER(ORDER BY Salary DESC) AS Row,Fname,State,Salary from Row_Number 

Row	Fname	State	Salary
1	Vijay	Delhi	23000
2	Neeraj	AP	16000
3	Raghu	UP	12000
4	Vipin	Delhi	10000
5	Chandra	Delhi	9000
6	Taslim	UP	8000
7	Jatin	MP	7000
8	Ravi	MP	6000
9	Manish	Delhi	5000

SELECT ROW_NUMBER() OVER(ORDER BY Salary ASC) AS Row,Fname,State,Salary from Row_Number 

Row	Fname	State	Salary
1	Manish	Delhi	5000
2	Ravi	MP	6000
3	Jatin	MP	7000
4	Taslim	UP	8000
5	Chandra	Delhi	9000
6	Vipin	Delhi	10000
7	Raghu	UP	12000
8	Neeraj	AP	16000
9	Vijay	Delhi	23000

Select Fname,State,Salary, ROW_NUMBER() OVER (PARTITION BY State Order by salary desc) as row from Row_Number 

Fname	State	Salary	row
Neeraj	AP	16000	1
Vijay	Delhi	23000	1
Vipin	Delhi	10000	2
Chandra	Delhi	9000	3
Manish	Delhi	5000	4
Jatin	MP	7000	1
Ravi	MP	6000	2
Raghu	UP	12000	1
Taslim	UP	8000	2

Bind Year in C#

#region BINDYEAR
    private void BINDYEAR()
    {
        try
        {
            int A = 1800;
            for (int i = 0; i < 20; i++)
            {
                ListItem LI = new ListItem();
                LI.Text = Convert.ToInt16(A).ToString();
                LI.Value = A.ToString();
                A=A+1;
                ddl_year.Items.Add(LI);
            }
            ddl_year.Items.Insert(0, "YYYY");
              
        }
        catch (Exception errmsg)
        {
            Response.Write(errmsg.Message.ToString());
        }
    }
    #endregion

SQL Command for set identity.

SET IDENTITY_INSERT [tblTest2] ON


SET IDENTITY_INSERT [tblTest2] OFF

Bulk Insert Query in SQL 2008

                             
                                             
CREATE TABLE Department
(
DepartmentID INT PRIMARY KEY,
DepartmentName VARCHAR(30)
)
******************************************************************
CREATE TYPE DeptType AS TABLE
(
DeptId INT, DeptName VARCHAR(30)
);

******************************************************************
CREATE PROCEDURE InsertDepartment
@InsertDept_TVP DeptType READONLY
AS
INSERT INTO Department(DepartmentID,DepartmentName)
SELECT * FROM @InsertDept_TVP;

DECLARE @DepartmentTVP AS DeptType;

INSERT INTO @DepartmentTVP(DeptId,DeptName)
VALUES (11,'Accounts'),
(12,'Purchase'),
(13,'Software'),
(14,'Stores'),
(15,'Maarketing');
*******************************************************************
EXEC InsertDepartment @DepartmentTVP;

Select query without using "Like" operator

.Select query without using "Like" operator . For eg select employee name start with 'j' and city is 'Noida' in company_name

select * from empdata where CHARINDEX('j',Employee_name)=1 and CHARINDEX('Noida',company_name)>0

Some SQL interview queries

1. To fetch ALTERNATE records from a table. (EVEN NUMBERED)select * from emp where rowid in (select decode(mod(rownum,2),0,rowid, null) from emp);
2. To select ALTERNATE records from a table. (ODD NUMBERED)select * from emp where rowid in (select decode(mod(rownum,2),0,null ,rowid) from emp);
3. Find the 3rd MAX salary in the emp table.select distinct sal from emp e1 where 3 = (select count(distinct sal) from emp e2 where e1.sal <= e2.sal);
4. Find the 3rd MIN salary in the emp table.select distinct sal from emp e1 where 3 = (select count(distinct sal) from emp e2where e1.sal >= e2.sal);
5. Select FIRST n records from a table.select * from emp where rownum <= &n;
6. Select LAST n records from a tableselect * from emp minus select * from emp where rownum <= (select count(*) - &n from emp);
7. List dept no., Dept name for all the departments in which there are no employees in the department.select * from dept where deptno not in (select deptno from emp); 
   alternate solution:  select * from dept a where not exists (select * from emp b where a.deptno = b.deptno);
   altertnate solution:  select empno,ename,b.deptno,dname from emp a, dept b where a.deptno(+) = b.deptno and empno is null;
8. How to get 3 Max salaries ?select distinct sal from emp a where 3 >= (select count(distinct sal) from emp b where a.sal <= b.sal) order by a.sal desc;
9. How to get 3 Min salaries ?select distinct sal from emp a  where 3 >= (select count(distinct sal) from emp b  where a.sal >= b.sal);
10. How to get nth max salaries ?
    select distinct hiredate from emp a where &n =  (select count(distinct sal) from emp b where a.sal >= b.sal);
11. Select DISTINCT RECORDS from emp table.select * from emp a where  rowid = (select max(rowid) from emp b where  a.empno=b.empno);
12. How to delete duplicate rows in a table?delete from emp a where rowid != (select max(rowid) from emp b where  a.empno=b.empno);
13. Count of number of employees in  department  wise.select count(EMPNO), b.deptno, dname from emp a, dept b  where a.deptno(+)=b.deptno  group by b.deptno,dname;
14.  Suppose there is annual salary information provided by emp table. How to fetch monthly salary of each and every employee?
    select ename,sal/12 as monthlysal from emp;
15. Select all record from emp table where deptno =10 or 40.
    select * from emp where deptno=30 or deptno=10;
16. Select all record from emp table where deptno=30 and sal>1500.
    select * from emp where deptno=30 and sal>1500;
17. Select  all record  from emp where job not in SALESMAN  or CLERK.
    select * from emp where job not in ('SALESMAN','CLERK');
18. Select all record from emp where ename in 'BLAKE','SCOTT','KING'and'FORD'.
    select * from emp where ename in('JONES','BLAKE','SCOTT','KING','FORD');
19. Select all records where ename starts with ‘S’ and its lenth is 6 char.
    select * from emp where ename like'S____';
20. Select all records where ename may be any no of  character but it should end with ‘R’.
    select * from emp where ename like'%R';
21. Count  MGR and their salary in emp table.
    select count(MGR),count(sal) from emp;
22. In emp table add comm+sal as total sal  .
    select ename,(sal+nvl(comm,0)) as totalsal from emp;
23. Select  any salary <3000 from emp table. 
    select * from emp  where sal> any(select sal from emp where sal<3000);
24. Select  all salary <3000 from emp table. 
    select * from emp  where sal> all(select sal from emp where sal<3000);
25. Select all the employee  group by deptno and sal in descending order.
    select ename,deptno,sal from emp order by deptno,sal desc;
26. How can I create an empty table emp1 with same structure as emp?
    Create table emp1 as select * from emp where 1=2;
27. How to retrive record where sal between 1000 to 2000?
    Select * from emp where sal>=1000 And  sal<2000
28. Select all records where dept no of both emp and dept table matches.
    select * from emp where exists(select * from dept where emp.deptno=dept.deptno)
29. If there are two tables emp1 and emp2, and both have common record. How can I fetch all the recods but common records only once?
    (Select * from emp) Union (Select * from emp1)
30. How to fetch only common records from two tables emp and emp1?
    (Select * from emp) Intersect (Select * from emp1)
31.  How can I retrive all records of emp1 those should not present in emp2?
    (Select * from emp) Minus (Select * from emp1)
32. Count the totalsa  deptno wise where more than 2 employees exist.
    SELECT  deptno, sum(sal) As totalsal
    FROM emp
    GROUP BY deptno
    HAVING COUNT(empno) > 2