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CDaoRelationInfo Structure

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The latest version of this topic can be found at CDaoRelationInfo Structure.

The CDaoRelationInfo structure contains information about a relation defined between fields of two tables in a CDaoDatabase object.

Syntax

struct CDaoRelationInfo  
{  
    CDaoRelationInfo();
*// Constructor  
    CString m_strName;      // Primary  
    CString m_strTable;     // Primary  
    CString m_strForeignTable;              // Primary  
    long m_lAttributes;     // Secondary  
    CDaoRelationFieldInfo* m_pFieldInfos;   // Secondary  
    short m_nFields;        // Secondary *// Below the // Implementation comment: *// Destructor, not otherwise documented  
};

Parameters

m_strName
Uniquely names the relation object. For more information, see the topic "Name Property" in DAO Help.

m_strTable
Names the primary table in the relation.

m_strForeignTable
Names the foreign table in the relation. A foreign table is a table used to contain foreign keys. Generally, you use a foreign table to establish or enforce referential integrity. The foreign table is usually on the many side of a one-to-many relationship. Examples of foreign tables include tables containing codes for the American states or Canadian provinces or customer orders.

m_lAttributes
Contains information about the relation type. The value of this member can be any of the following:

  • dbRelationUnique Relationship is one-to-one.

  • dbRelationDontEnforce Relationship is not enforced (no referential integrity).

  • dbRelationInherited Relationship exists in a noncurrent database that contains the two attached tables.

  • dbRelationLeft The relationship is a left join. A left outer join includes all of the records from the first (left-hand) of two tables, even if there are no matching values for records in the second (right-hand) table.

  • dbRelationRight The relationship is a right join. A right outer join includes all of the records from the second (right-hand) of two tables, even if there are no matching values for records in the first (left-hand) table.

  • dbRelationUpdateCascade Updates will cascade.

  • dbRelationDeleteCascade Deletions will cascade.

m_pFieldInfos
A pointer to an array of CDaoRelationFieldInfo structures. The array contains one object for each field in the relation. The m_nFields data member gives a count of the array elements.

m_nFields
The number of CDaoRelationFieldInfo objects in the m_pFieldInfos data member.

Remarks

The references to Primary and Secondary above indicate how the information is returned by the GetRelationInfo member function in class CDaoDatabase.

Relation objects are not represented by an MFC class. Instead, the DAO object underlying an MFC object of the CDaoDatabase class maintains a collection of relation objects: CDaoDatabase supplies member functions to access some individual items of relation information, or you can access them all at once with a CDaoRelationInfo object by calling the GetRelationInfo member function of the containing database object.

Information retrieved by the CDaoDatabase::GetRelationInfo member function is stored in a CDaoRelationInfo structure. CDaoRelationInfo also defines a Dump member function in debug builds. You can use Dump to dump the contents of a CDaoRelationInfo object.

Requirements

Header: afxdao.h

See Also

CDaoRelationFieldInfo Structure