These constants are used to determine how individual parameters are to be handled when used in parameter queries.
| Constant | Value | Description |
| rdParamInput | 0 | (Default) The parameter is used to pass information to the procedure. |
| rdParamInputOutput | 1 | The parameter is used to pass information both to and from the procedure. |
| rdParamOutput | 2 | The parameter is used to return information from the procedure as in an output parameter in SQL. |
| rdParamReturnValue | 3 | The parameter is used to pass the return value from a procedure. |