CdbParameter Object

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A CdbParameter object represents a value supplied to a query. The parameter is associated with a CdbQueryDef object created from a parameter query.

Remarks

CdbParameter objects allow you to change the arguments in a frequently run CdbQueryDef object without having to recompile the query.

Using the properties of a CdbParameter object, you can set a query parameter that can be changed before the query is run. You can:

• Use the Name property to return the name of a parameter.
  
  
• Use the Value property to set or return the parameter values to be used in the query.
  
  
• Use the Type property to return the data type of the CdbParameter object.
  
  
• Use the Direction property to set or return whether the parameter is an input parameter, an output parameter, or both.

In an ODBCDirect workspace, you can also:

• Change the setting of the Type property. Doing so will also clear the Value property.
  
  
• Use the Direction property to set or return whether the parameter is an input parameter, an output parameter, or both.

CdbParameter Constructor Syntax

Use any one of the following three constructors. The qualifier 'CONSTRUCTOR' in the syntax models is provided to help readability. It has no syntactic value.

CONSTRUCTORCdbParameter(VOID);

This constructor creates an instance of the class. There are no parameters.

CONSTRUCTORCdbParameter(const CdbParameter &);

This constructor creates a copy of the object referenced in the parameter.

CONSTRUCTORCdbParameter(DAOParameter *pprm,

BOOL bAddRef = FALSE);

DAO functionality is presented through pointers to DAO Automation interfaces. This constructor makes a DAO interface available in the form of a DAO class object that provides additional functionality.

This constructor is not required for typical use. It is provided to enable you to easily create a DAO class object if you have access to the corresponding DAO interface.

When the destructor for the DAO object is invoked, the underlying Automation interface's Release member is called. If Release decrements the interface's reference count to zero, the pointer to the Automation interface can be deleted. If you don't want this to happen (for example, because you want to discard the DAO object, but continue using the Automation interface), specify TRUE for the second parameter. The underlying Automation interface's AddRef member is called, which counterbalances the eventual call to Release.