Uses of XPath language

XPath is a language defined by the W3C. It used to select nodes from XML documents. 


Microsoft SQL Server 2000 supports XPath language that helps to retrieve data from XML documents. 


Microsoft SQL server uses a mapping schema to define an XML based view of the data in one or more SQL Server tables and views. The mapping schema is then used to retrieve data.

Constraints for Designing of Files and File groups in Microsoft SQL Server

There are some constraints for designing files and file group in Microsoft SQL server. These constraints are following :


A file or file group can only be used by one database. For example, the files abcd.mdf and abcd.ndf contains data and objects for abc database, cannot be used by any other database.

A file can be a member of only one file group.


Data and transaction log information cannot be part of the same file or file group.

Transaction log files can't be part of a file group.

Types of Authentication Modes in Microsoft SQL Server

There are two types of Authentication modes in Microsoft SQL Server. These are following :

• Windows Authentication
• Mixed mode

Windows authentication mode

Windows authentication mode allows users to connect using Windows domain like NT/2000 account. The access to the Microsoft SQL server is controlled by Windows NT/2000 account or group used when logged in, means that Windows username and password are used to access the database on Microsoft SQL Server server.

Mixed mode authentication

Mixed mode authentication allows use of Windows credentials and the local Microsoft SQL server account to logged into Database.

DDL DCL and DML in Microsoft SQL Server

Data definition language

Data definition language (DDL) is used to define and manage all attributes and properties of a database in Microsoft SQL Server. DDL statements include following commands :

• CREATE
• ALTER
• DROP

Data Control Language

Data control language (DCL) is used to control permissions on database objects. Permissions are controlled by using following commands :

• GRANT
• REVOKE
• DENY

Data Manipulation Language

Data manipulation language (DML) is used to select, insert, update, and delete data in the objects defined with Data Definition Language.

Why Avoid Permitting NULL values in Microsoft SQL Server

NULL value in column in Microsoft SQL Server means that no entry has been made into the column. It states that the corresponding value is either unknown or undefined. It is also different from zero or "". 

We should avoid permitting null values because Column with NULL values can't have PRIMARY KEY constraints. Certain calculations can be inaccurate if NULL columns are involved.