The SQL_ARD_TYPE type identifier is used to indicate that the data in a buffer will be of the type specified in the SQL_DESC_CONCISE_TYPE field of the ARD. SQL_ARD_TYPE is entered in the TargetType argument of a call to SQLGetData instead of a specific data type, and enables an application to change the data type of the buffer by changing the descriptor field. This value ties the data type of the *TargetValuePtr buffer to the descriptor field. (SQL_ARD_TYPE is not entered in a call to SQLBindCol or SQLBindParameter because the type of the bound buffer is already tied to the SQL_DESC_TYPE and SQL_DESC_CONCISE_TYPE fields, and can be changed at any time by changing either of those fields.)
The SQL_ARD_TYPE type identifier can be used to specify non-default values for leading precision and seconds precision of interval data types, and precision and scale values for the SQL_C_NUMERIC data type. For more information, see “Overriding Default Leading and Seconds Precision for Interval Data Types” and “Overriding Default Precision and Scale for Numeric Data Types” later in this appendix.