delp025.html

对于学习很有帮助

          <br>
          <br>
          query2.next;<br>
          <br>
          　　end;<br>
          <br>
          <br>
          <br>
          <strong>五、lookup字段的使用<br>
          <br>
          </strong>　　在实际的数据库程序中，我们经常使用编码表，例如对消费品名进行编码，在存入消费库中时使用消费品编码，而在使用DBGRID或其他数据明了构件显示出来时使用具体内容。这就要使用lookup字段了。<br>
          <br>
          <br>
          <br>
          　　我们可以作以下试验:<br>
          <br>
          　　(1）新建一个项目，使用database desktop建两个库，别名test，如下:<br>
          <br>
          　　nameid:编码表</p>
        <br>
        <table border="0" style="font-size: 9pt" cellspacing="1" cellpadding="0" bgcolor="6699cc" width="95%" align="center">
          <br>
          <tbody> <br>
          <tr> <br>
            <td align="middle">字段名</td>
            <br>
            <td align="middle">Name</td>
            <br>
            <td align="middle">Id</td>
            <br>
          </tr>
          <br>
          <tr bgcolor="#FFFFFF"> <br>
            <td align="middle">记录1</td>
            <br>
            <td align="middle">Tanglu</td>
            <br>
            <td align="middle">1</td>
            <br>
          </tr>
          <br>
          <tr bgcolor="#FFFFFF"> <br>
            <td align="middle">记录2</td>
            <br>
            <td align="middle">shangwang</td>
            <br>
            <td align="middle">2</td>
            <br>
          </tr>
          <br>
          </tbody> <br>
        </table>
        <br>
        <p>　　id:欲存入表(现为空）</p>
        <br>
        <table border="0" style="font-size: 9pt" cellspacing="1" width="596" bgcolor="6699cc" cellpadding="0" align="center">
          <br>
          <tbody> <br>
          <tr> <br>
            <td align="middle" width="291">字段名</td>
            <br>
            <td align="middle" width="295">Id</td>
            <br>
          </tr>
          <br>
          <tr bgcolor="#FFFFFF"> <br>
            <td align="middle" width="291">记录1</td>
            <br>
            <td align="middle" width="295">　</td>
            <br>
          </tr>
          <br>
          <tr bgcolor="#FFFFFF"> <br>
            <td align="middle" width="291">记录2</td>
            <br>
            <td align="middle" width="295">　</td>
            <br>
          </tr>
          <br>
          </tbody> <br>
        </table>
        <br>
        <p><br>
          <br>
          　　在Form1上放如下构件:</p>
        <br>
        <table border="0" style="font-size: 9pt" cellspacing="1" width="95%" bgcolor="6699cc" cellpadding="0" align="center">
          <br>
          <tbody> <br>
          <tr> <br>
            <td height="16" width="34%">table1</td>
            <br>
            <td height="16" width="66%">指向nameid表,即databasename=test; tablename=nameid;</td>
            <br>
          </tr>
          <br>
          <tr bgcolor="#FFFFFF"> <br>
            <td width="34%">Datasource1</td>
            <br>
            <td width="66%">指向table1,即dataset=table1</td>
            <br>
          </tr>
          <br>
          <tr bgcolor="#FFFFFF"> <br>
            <td height="12" width="34%">table2</td>
            <br>
            <td height="12" width="66%">指向id表,即databasename=test; tablename=id;</td>
            <br>
          </tr>
          <br>
          <tr bgcolor="#FFFFFF"> <br>
            <td width="34%">Datasource2</td>
            <br>
            <td width="66%">指向table2,即dataset=table2</td>
            <br>
          </tr>
          <br>
          <tr bgcolor="#FFFFFF"> <br>
            <td width="34%">dbgrid1</td>
            <br>
            <td width="66%">指向table2,即dataSource=dataSource2</td>
            <br>
          </tr>
          <br>
          </tbody> <br>
        </table>
        <br>
        <p align="left"><br>
          <br>
          　　(2）双击table2，弹出字段编辑器，在字段编辑器上右击，选择“addfields...＂，加入“id＂字段;再选择“newfield...＂。这时弹出newfield对话框，如下填写:</p>
        <br>
        <table border="0" cellspacing="1" style="font-size: 9pt" width="95%" bgcolor="6699cc" cellpadding="0" align="center">
          <br>
          <tbody> <br>
          <tr> <br>
            <td align="middle" height="16">name</td>
            <br>
            <td align="middle" height="16">type</td>
            <br>
            <td align="middle" height="16">Field type</td>
            <br>
            <td align="middle" height="16">Key fields</td>
            <br>
            <td align="middle" height="16">dataset</td>
            <br>
            <td align="middle" height="16">Lookup keys</td>
            <br>
            <td align="middle" height="16">Result field</td>
            <br>
          </tr>
          <br>
          <tr bgcolor="#FFFFFF"> <br>
            <td align="middle" height="18">test</td>
            <br>
            <td align="middle" height="18">string</td>
            <br>
            <td align="middle" height="18">ookup</td>
            <br>
            <td align="middle" height="18">Id</td>
            <br>
            <td align="middle" height="18">Table1</td>
            <br>
            <td align="middle" height="18">id</td>
            <br>
            <td align="middle" height="18">name</td>
            <br>
          </tr>
          <br>
          </tbody> <br>
        </table>
        <br>
        <p align="left"><br>
          <br>
          　　(3）将table1和table2的active属性置为true，编译运行。<br>
          <br>
          　　这时可以看出，从test字段下拉出姓名，选定一个后，存入id字段的是其编码，这样就达到了目的。</p>
        <div align=right></div>
                        </center>
      <!-- #EndEditable --></td>
  </tr>
  <tr>
    <td width="582"><!-- #BeginEditable "%B1%B8%D7%A2" --><!-- #EndEditable --></td>
  </tr>
</table>

<br>
<hr size="1">
<table width="25%" border="1" align="center" cellspacing="0" cellpadding="0" bordercolorlight="#CCCCFF" bordercolordark="#000033" bordercolor="#6666FF">
  <tr align="center"> 
    <td> 转载请注明出于 <a href="http://fwolf.yeah.net" target="_blank">独孤之所</a><!--Fwolf出品
[e-mail]
http://fwolf.yeah.net --> </td>
  </tr>
  <tr align="center"> 
    <td> 
      <script>document.write("<a href=http://www.topcn.com/siteinfo.asp?UserName=fwolf2000&SiteType=0 target=_blank><img src=http://www1.topcn.com:8081/statistics.asp?fwolf2000&referURL="+escape(top.document.referrer)+"&curURL="+escape(top.document.URL)+"&imgStyle=0"+" border=0 alt='Top中文网站龙虎榜' ></a>");</script>
      <script>document.write("<a href=http://www.textclick.com/viewmain.asp?name=fwolf2000 target=_blank><img src=http://ad.t2t2.com/stat.asp?user=fwolf2000&refer="+escape(document.referrer)+"&cur="+escape(document.URL)+" alt=太极统计 border=0></a>");</script>
    </td>
  </tr>
</table>
<table width="100%" border="0" align="center" cellspacing="1" bgcolor="#66FF66">
  <tr> 
    <td width="10%"><a href="javascript:window.close()">[关闭窗口]</a></td>
    <td width="90%"> 
      <div align="left"></div>
    </td>
  </tr>
</table>
<div id="Layer1" style="position:absolute; width:470px; height:60; z-index:1; left: 293px; top: 13px; overflow: hidden"> 
  <table width="100%" border="0" cellspacing="0" cellpadding="0" height="60">
    <tr> 
      <td><a href="http://202.99.67.100/adclick2/click/random.cgi?job=go&id=1490" target="_blank"><img src="http://202.99.67.100/adclick2/click/random.cgi?id=1490" border="0" width="468" height="60"></a> 
      </td>
    </tr>
  </table>
</div>
<div align="center"></div>
<p align="center"> 
<script language="JavaScript1.1" src=http://ad.t2t2.com/textclick.asp?user=fwolf&style=4&bkcolor=no></script>
</p>
<p align="center">&nbsp; </p>
</body>
<!-- #EndTemplate --></html>