CAST vs CONVERT in Sql Server

CAST() Function:

The Cast() function is used to convert a data type variable or data from one data type to another data type.

The Cast() function provides a data type to a dynamic parameter (?) or a NULL value.

Syntax:

CAST ( [Expression] AS Datatype)

 
CONVERT() Function:

When you convert expressions from one type to another, in many cases there will be a need within a stored procedure or other routine to convert data from a date time type to a varchar type. The Convert function is used for such things. The CONVERT() function can be used to display date/time data in various formats.

Syntax:

CONVERT(data_type(length), expression, style)
 
The basic differences are
  
     Cast:

    Cast is  ANSII Standard
    Cast cannot be used for Formatting Purposes.
    Cast cannot convert a datetime to specific format

    Convert

    Convert is Specific to SQL SERVER
    Convert can be used for Formatting Purposes.For example Select convert (varchar, datetime, 101)
    Convert can be used to convert a datetime to specific format

   
  
Examples:

CAST:

SELECT CAST ( 10.20 AS INT )

Output
10

Above example converts 10.20 float value into an integer value and returns 10.

CONVERT:

CONVERT(VARCHAR(19),GETDATE())

O/p:Nov 04 2011 11:45 PM

CONVERT(VARCHAR(10),GETDATE(),10)
O/p:11-04-11