|GNADE User's Guide: GNADE, The GNat Ada Database Environment; Version 1.5.3; Document Revision $Revision: 1.45 $|
This chpater gives an overview of the concepts of the ADBC interface.
The ADBC interface is based upon the following major components:
Host variables are used to transfer data between the data base and the application. In a query the hostvariables are indicated by a name preceeded by an ':' in a query. The API allowes to associcate Ada 95 host variables with these names. An Ada 95 hostvariable provides the value and the additional attribute Is_Null to the application programmer, which means the variable is has a value or is not set.
Driver dependencies: Not all database drivers do provide the null indication for a colon in the result set. As a consequence the driver may not be able to support this. The driver should always return true and a defined value.