Using Type Indicators When Getting and Setting Data
Most consumers, when they allocate memory in which to get or set data, use the type that corresponds to the indicator returned by IColumnsInfo::GetColumnInfo for the column. When a consumer gets or sets data according to the type returned by GetColumnInfo, the provider guarantees it can always transfer the data safely. The consumer specifies this indicator in the wType element of the DBBINDING structure used to bind the memory.
The consumer can allocate and bind memory of a different type only if the provider supports conversion between that type and the type returned by GetColumnInfo. For more information, see Data Type Conversion.