In SQL Server, each column, local variable, expression, and parameter has a related data type.
A data type is an attribute that specifies the type of data that the object can hold: integer data, character data, monetary data, date and time data, binary strings, and so on.
SQL Server supplies a set of system data types that define all the types of data that can be used with SQL Server. You can also define your own data types in Transact-SQL or the Microsoft .NET Framework.
Alias data types are based on the system-supplied data types.
For more information about alias data types, see CREATE TYPE (Transact-SQL).
User-defined types obtain their characteristics from the methods and operators of a class that you create by using one of the programming languages support by the .NET Framework.
- The “Cursor” and “Table” data types are not supported in the table columns.
- The three variables (Text, nText and Image) will be removed in future version of SQL Server 2012.