book_text9.htm

深入编程内幕vc++ 非常适合处学者学习

            lang=EN-US><O:P> </O:P></SPAN></SPAN></P>
            <P class=MsoNormal 
            style="WORD-BREAK: break-all; mso-line-height-alt: 1.3pt; mso-layout-grid-align: none; punctuation-wrap: simple"><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; BACKGROUND: #d9d9d9; FONT-FAMILY: 'Courier New'; mso-bidi-font-size: 10.0pt; mso-bidi-font-family: 'Times New Roman'; mso-shading: white; mso-pattern: gray-15 black">TableInfo_&gt;Append();<O:P> 
            </O:P></SPAN></P>
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            style="WORD-BREAK: break-all; mso-line-height-alt: 1.3pt; mso-layout-grid-align: none; punctuation-wrap: simple"><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">下面介绍如何进行数据库操作：</SPAN><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt"><O:P> 
            </O:P></SPAN></P>
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            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">首先生成记录集对象：<SPAN 
            lang=EN-US><O:P> </O:P></SPAN></SPAN></P>
            <P class=MsoNormal 
            style="WORD-BREAK: break-all; mso-line-height-alt: 1.3pt; mso-layout-grid-align: none; punctuation-wrap: simple"><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; BACKGROUND: #d9d9d9; FONT-FAMILY: 'Courier New'; mso-bidi-font-size: 10.0pt; mso-bidi-font-family: 'Times New Roman'; mso-shading: white; mso-pattern: gray-15 black">Recordset 
            = new CDaoRecordset(newDatabase);<O:P> </O:P></SPAN></P>
            <P class=MsoNormal 
            style="WORD-BREAK: break-all; mso-line-height-alt: 1.3pt; mso-layout-grid-align: none; punctuation-wrap: simple"><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">然后使用</SPAN><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt">SQL</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">语句打开记录集对象。首先把</SPAN><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt">SQL</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">语句记入一个字符串：<SPAN 
            lang=EN-US><O:P> </O:P></SPAN></SPAN></P>
            <P class=MsoNormal 
            style="WORD-BREAK: break-all; mso-line-height-alt: 1.3pt; mso-layout-grid-align: none; punctuation-wrap: simple"><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; BACKGROUND: #d9d9d9; FONT-FAMILY: 'Courier New'; mso-bidi-font-size: 10.0pt; mso-bidi-font-family: 'Times New Roman'; mso-shading: white; mso-pattern: gray-15 black">CString<SPAN 
            style="mso-tab-count: 1">&nbsp;&nbsp;&nbsp; </SPAN>strQuery = 
            _T("Select * from student");<O:P> </O:P></SPAN></P>
            <P class=MsoNormal 
            style="WORD-BREAK: break-all; mso-line-height-alt: 1.3pt; mso-layout-grid-align: none; punctuation-wrap: simple"><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">使用这个字符串打开记录集。<SPAN 
            lang=EN-US><O:P> </O:P></SPAN></SPAN></P>
            <P class=MsoNormal 
            style="WORD-BREAK: break-all; mso-line-height-alt: 1.3pt; mso-layout-grid-align: none; punctuation-wrap: simple"><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; BACKGROUND: #d9d9d9; FONT-FAMILY: 'Courier New'; mso-bidi-font-size: 10.0pt; mso-bidi-font-family: 'Times New Roman'; mso-shading: white; mso-pattern: gray-15 black">Recordset_&gt;Open(dbOpenDynaset 
            , strQuery);<SPAN style="mso-tab-count: 1">&nbsp;&nbsp;&nbsp; 
            </SPAN><O:P></O:P></SPAN></P>
            <P class=MsoNormal 
            style="WORD-BREAK: break-all; mso-line-height-alt: 1.3pt; mso-layout-grid-align: none; punctuation-wrap: simple"><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 'Courier New'; mso-bidi-font-size: 10.0pt; mso-bidi-font-family: 'Times New Roman'">dbOpenDynaset</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'Courier New'; mso-ascii-font-family: 'Courier New'">参数的意思是表示记录集打开的类型。</SPAN><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 'Courier New'; mso-bidi-font-size: 10.0pt; mso-bidi-font-family: 'Times New Roman'">dbOpenDynaset</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'Courier New'; mso-ascii-font-family: 'Courier New'">的意思是打开一个</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">可以双向滚动的动态记录集。这个记录集中的记录是使用我们定义的</SPAN><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt">SQL</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">语句对数据库进行查询得到的。这个参数还有另外的两种选择：</SPAN><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt"><O:P> 
            </O:P></SPAN></P>
            <P class=MsoNormal 
            style="WORD-BREAK: break-all; mso-line-height-alt: 1.3pt; mso-layout-grid-align: none; punctuation-wrap: simple"><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt">dbOpenTable</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">参数指示打开一个数据表类型的记录集，使用这种类型的记录集只能对单一的数据库中的记录进行操纵。</SPAN><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt"><O:P> 
            </O:P></SPAN></P>
            <P class=MsoNormal 
            style="WORD-BREAK: break-all; mso-line-height-alt: 1.3pt; mso-layout-grid-align: none; punctuation-wrap: simple"><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'">如果使用</SPAN><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt">dbOpenSnapshot</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">参数表示打开的是映像记录集，</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'">它实际上是所选择的记录集的一个静态的拷贝，在只需要进行查询操作或者希望制作报表的时候，使用这种记录集比较合适，它不会对数据库中的数据进行修改。</SPAN><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt"><O:P> 
            </O:P></SPAN></P>
            <P class=MsoNormal 
            style="TEXT-INDENT: 21.25pt; mso-line-height-alt: 1.3pt"><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'">接下来对记录集当中的一个标志位赋值，说明是否要求自动地标记出</SPAN><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt">CACHE</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'">当中经改变的记录。</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">使用记录集的时候是</SPAN><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt">DAO</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">把被检索出的记录读入</SPAN><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt">CACHE</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'">，</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">所有的操纵都是针对</SPAN><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt">CACHE</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">中的记录进行的，要实现对数据库当中的记录更新必须把</SPAN><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt">CACHE</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">记录中被改变的字段的值写回到数据库文件当中去。这个标志位的作用就是当</SPAN><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt">CACHE</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">中的数据改变的时候，是否需要自动的</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'">标</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">记出记录中那些应该被写回的字段。</SPAN><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt"><O:P> 
            </O:P></SPAN></P>
            <P class=MsoNormal 
            style="WORD-BREAK: break-all; TEXT-INDENT: 21.25pt; mso-line-height-alt: 1.3pt; mso-layout-grid-align: none; punctuation-wrap: simple"><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">下面介绍如何填加一个记录。<SPAN 
            lang=EN-US><O:P> </O:P></SPAN></SPAN></P>
            <P class=MsoNormal 
            style="WORD-BREAK: break-all; TEXT-INDENT: 21.25pt; mso-line-height-alt: 1.3pt; mso-layout-grid-align: none; punctuation-wrap: simple"><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt">&nbsp;<O:P> 
            </O:P></SPAN></P>
            <P class=MsoNormal 
            style="WORD-BREAK: break-all; mso-line-height-alt: 1.3pt; mso-layout-grid-align: none; punctuation-wrap: simple"><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; BACKGROUND: #d9d9d9; FONT-FAMILY: 'Courier New'; mso-bidi-font-size: 10.0pt; mso-bidi-font-family: 'Times New Roman'; mso-shading: white; mso-pattern: gray-15 black">m_Recordset 
            _&gt;AddNew();<O:P> </O:P></SPAN></P>
            <P class=MsoNormal 
            style="WORD-BREAK: break-all; mso-line-height-alt: 1.3pt; mso-layout-grid-align: none; punctuation-wrap: simple"><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; BACKGROUND: #d9d9d9; FONT-FAMILY: 'Courier New'; mso-bidi-font-size: 10.0pt; mso-bidi-font-family: 'Times New Roman'; mso-shading: white; mso-pattern: gray-15 black">m_Recordset_&gt;Update();<O:P> 
            </O:P></SPAN></P>
            <P class=MsoNormal 
            style="WORD-BREAK: break-all; TEXT-INDENT: 21.25pt; mso-line-height-alt: 1.3pt; mso-layout-grid-align: none; punctuation-wrap: simple"><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">使用</SPAN><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt">AddNew()</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">这个函数可以在数据表记录集或者是动态记录集当中添加新的记录，调用</SPAN><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt">AddNew()</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">之后必须接着调用</SPAN><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt">Update()</SPAN><SPAN 
            style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.0pt; mso-hansi-font-family: 'MS Sans Serif'">来确认这个添加动作，将新的记录保存到数据库文件当中去。新的记录在数据库当中的位置取决于当前记录集的类型：如果是动态记录集，新记录都将被插入到记录集的末尾。如果是数据表记录集的话，当数据库表中定义了主键的时候新记录将按照库表的排序规则插入到合适的地方；如果没有定义主键那么新记录也会被插入到记录集的末尾。</SPAN><SPAN 
            lang=EN-US 
            style="FONT-SIZE: 10.5pt; mso-bidi-font-size: 10.0pt"><O:P> 
            </O:P></SPAN></P>
            <P class=MsoNormal 
            style="WORD-BREAK: break-all; TEXT-INDENT: 21.25pt; mso-line-height-alt: 1.3pt; mso-layout-grid-align: none; punctuation-wrap: simple"><SPAN