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What is an Index?

Posted By :Shashi Ray     Posted Date :October 03, 2008    Points :10   Category :Sql Server 
When queries are run against a db, an index on that db basically helps in the way the data is sorted to process the query for faster and data retrievals are much faster when we have an index.

You can also find related Interview Question to What is an Index?  below: 

What is a Index?

  
To execute the Quesry faster (More...)

What is Index?

  
An index is a physical structure containing pointers to the data. Indices are created in an existing table to locate rows more quickly and efficiently. It is possible to create an index on one or more columns of a table, and each index is given a name. The users cannot see the indexes; they are just used to speed up queries. Effective indexes are one of the best ways to improve performance in a database application. A table scan happens when there is no index available to help a query. In a table scan SQL Server examines every row in the table to satisfy the query results. Table scans are sometimes unavoidable, but on large tables, scans have a terrific impact on performance

Shashi Ray (More...)

What does this error mean:
System.ArgumentOutOfRangeException: Index was out of range : Upgrading CRM 3.0

  
Error Message : "System.ArgumentOutOfRangeException: Index was out of range", occurs while upgrading Microsoft Dynamics CRM 3.0 to Microsoft Dynamics CRM 4.0

Solution : The problem occurs if an ampersand is in the subject of an activity that was created in a sales process or in a workflow rule. So, remove the ampersand.

To obtain this fix, use the Update Installation Files option during Microsoft Dynamics CRM 4.0 setup




For more details, visit http://kbalertz.com/Feedback.aspx?kbNumber=948917/ (More...)

Is it possible to create Cluster Index on Unique Key Column?

  
Unique key column by default creates a non-cluster index on the column. Primary key creates cluster index on the column. The only difference is Unique key column allows only one null value. So is it possible to have cluster index on Unique key column?

The answer is YES. Though Unique key allows null value but it still maintains the uniqueness of the column. (More...)

What will you do if you need to create clustered index on more than one field? Is it possible?

  
The answer is yes and no.
You can create clustered index only one clustered index in table.
Either you can create index on entire table or you can create clustered index on a view covering entire table.
Suppose, you have created table with following:
CREATE TABLE [dbo].[Table1](
[field1] [int] IDENTITY(1,1) NOT NULL,
[field2] [nchar](10) ,
[field3] [nchar](10) ,
[field4] [nchar](10)
) ON [PRIMARY]
Create index on entire table:
CREATE INDEX idx_coverTable ON Table1(field1, field2) INCLUDE (field3, field4)
Create clustered index on a view covering entire table:
CREATE VIEW v1111 with SCHEMABINDING
AS
SELECT field1, field2, field3, field4 FROM dbo.Table1
GO
CREATE UNIQUE CLUSTERED INDEX idx_viewClustered ON dbo.v1111(field1, field2, field3, field4)
GO (More...)

What is Index?

  
A database index is a data structure which use to improve the speed of operations on a database table.

It's a physical structure containing pointers to the data.

Index can be created using one or more columns of a database table.
Index are created in an existing table to quickly and efficiently lookups.

It is possible to create an index on one or more columns of a table, and each index is given a name.

There are two type of index available.

Clustered index :
Clustered index are physical form of sorting. Therefore only one clustered index can be created on each table because the data rows themselves can only be sorted in one order.

Non Clustered index :
Non clustered indexes are logical form of sorting. Therefore more than one Non clustered indexes can be created on each table. (More...)

What is an Index? -

  
When queries are run against a db, an index on that db basically helps in the way the data is sorted to process the query for faster and data retrievals are much faster when we have an index. (More...)

What is the basic difference between clustered and a non-clustered index

  
The difference is that, Clustered index is unique for any given table and we can have only one clustered index on a table. The leaf level of a clustered index is the actual data and the data is resorted in case of clustered index. Whereas in case of non-clustered index the leaf level is actually a pointer to the data in rows so we can have as many non-clustered indexes as we can on the db. (More...)

How can we find the index of current selection in BindingSource Class?

  
Using bindingSource1.Position we can find the index of currently selected item.
Here bindingSource1 is the object of BindingSource Class. (More...)

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