Index

Create Clustered index

With a clustered index the leaf pages contain the actual table rows. Therefore, there can be only one clustered index.

CREATE TABLE Employees
(
    ID CHAR(900),
    FirstName NVARCHAR(3000),
    LastName NVARCHAR(3000),
    StartYear CHAR(900)
)
GO

CREATE CLUSTERED INDEX IX_Clustered 
ON Employees(ID)
GO

Create Non-Clustered index

Non-clustered indexes have a structure separate from the data rows. A non-clustered index contains the non-clustered index key values and each key value entry has a pointer to the data row that contains the key value. There can be maximum 999 non-clustered index on SQL Server 2008/ 2012.

Link for reference: https://msdn.microsoft.com/en-us/library/ms143432.aspx

CREATE TABLE Employees
(
    ID CHAR(900),
    FirstName NVARCHAR(3000),
    LastName NVARCHAR(3000),
    StartYear CHAR(900)
)
GO

CREATE NONCLUSTERED INDEX IX_NonClustered
ON Employees(StartYear)
GO

Show index info

SP_HELPINDEX tableName

Index on view

CREATE VIEW  View_Index02
WITH SCHEMABINDING
AS 
SELECT c.CompanyName, o.OrderDate, o.OrderID, od.ProductID 
     FROM dbo.Customers C 
        INNER JOIN dbo.orders O ON c.CustomerID=o.CustomerID  
            INNER JOIN dbo.[Order Details] od ON o.OrderID=od.OrderID   
GO

CREATE UNIQUE CLUSTERED INDEX IX1 ON 
    View_Index02(OrderID, ProductID)

Drop index

DROP INDEX IX_NonClustered ON Employees

Returns size and fragmentation indexes

sys.dm_db_index_physical_stats (   
    { database_id | NULL | 0 | DEFAULT }  
  , { object_id | NULL | 0 | DEFAULT }  
  , { index_id | NULL | 0 | -1 | DEFAULT }  
  , { partition_number | NULL | 0 | DEFAULT }  
  , { mode | NULL | DEFAULT }  
)  


Sample :

SELECT * FROM sys.dm_db_index_physical_stats  
    (DB_ID(N'DBName'), OBJECT_ID(N'IX_NonClustered '), NULL, NULL , 'DETAILED');

Reorganize and rebuild index

avg_fragmentation_in_percent value	Corrective statement
>5% and < = 30%	REORGANIZE
>30%	REBUILD

ALTER INDEX IX_NonClustered ON tableName REORGANIZE;  


ALTER INDEX ALL ON Production.Product
 REBUILD WITH (FILLFACTOR = 80, SORT_IN_TEMPDB = ON,
          STATISTICS_NORECOMPUTE = ON);

Rebuild or reorganize all indexes on a table

Rebuilding indexes is done using the following statement

ALTER INDEX All ON tableName REBUILD;

This drops the index and recreates it, removing fragementation, reclaims disk space and reorders index pages.

One can also reorganize an index using

ALTER INDEX All ON tableName REORGANIZE;

which will use minimal system resources and defragments the leaf level of clustered and nonclustered indexes on tables and views by physically reordering the leaf-level pages to match the logical, left to right, order of the leaf nodes

Rebuild all index database

EXEC sp_MSForEachTable 'ALTER INDEX ALL ON ? REBUILD'

Index investigations

You could use “SP_HELPINDEX Table_Name”, but Kimberly Tripp has a stored procedure (that can be found here), which is better example, as it shows more about the indexes, including columns and filter definition, for example:
Usage:

USE Adventureworks 
EXEC sp_SQLskills_SQL2012_helpindex 'dbo.Product'

Alternatively, Tibor Karaszi has a stored procedure (found here). The later will show information on index usage too, and optionally provide a list of index suggestions. Usage:

USE Adventureworks 
EXEC sp_indexinfo 'dbo.Product'