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.hen two expressions that have different data types, collations, precision, scale, or length are combined by an operator, the characteristics of result are determined by the following: The data type of the result is determined by applying the rules of data type precedence to the data types of the input expressions.