5.6.3 Indexing Using a Key

Exept for the Insert() container, the keys are created out of the primary keys, thus avoiding duplicates.

A “key” always contains the following parts:

Ø                                                       K-@@ (start delimiter)

Ø                                                       PK1      (the primary key value from the database)

Ø                                                       @@      (primary key delimiter, only for tables with constraint PK)

Ø                                                       PK2      (the constraint primary key value from the database)

Ø                                                       etc.

(See example in Picture 12: Indexing Using a Key)

You can always retrieve the key using the GetIndexKey() method. This is extremely useful if you want to access a Update() or Delete() container from a Select() container. Another way of retrieving the key is by calling the ItemKeyAt() method on the container.

119:    std::stringstream text;

120:

121:    // Perform a simple select on the "DeclarationType" table belonging to the

122:    // "m_pDBGenType" Table Set

123:    clsCollDeclarationType* pCollDeclType = clsDeclarationType::Select(m_pDBGenType);

124:

125:    if (pCollDeclType != NULL)

126:    {

127:       // Index the items in the collection using a key

128:       // Exceed the max item count to get an error for the last two items

129:       int itemCount = pCollDeclType->Count();

130:       for ( long lIndex = 0; lIndex < itemCount + 2; lIndex++ )

131:       {

132:          DBString::clsDBString strKey;

133:          strKey << DBGlobalDeclaration::C_INDEX_KEY_HEADER << lIndex;

134:          clsDeclarationType* pDeclType = pCollDeclType->Item(strKey);

135:

136:          if (pDeclType != NULL)

137:          {

138:             text << "Key: " << pDeclType->GetIndexKey() << ", Item: " <<

139:                pDeclType->DB_DeclarationType() << std::endl;

140:          }

141:          else

142:          {

143:             text << "Key: " << strKey << " not found!" << std::endl;

144:          }

145:       }

146:    }

Picture 12: Indexing Using a Key

Related Topics

5.6 Table Container