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<td width="109" align="center" class="p2"><font color="#FFFFFF"><b>Access
2000</b></font><font color="#FF3333" ><b></b></font></td>
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<p><span class="p1"><font color="#0000CC"><img src="img/small.gif" width="12" height="12">
<a href="ac2k0101.htm">初识Access 2000<br>
</a></font><font color="#0000CC"> </font></span><span class="p1"><font color="#0000CC"><img src="img/small.gif" width="12" height="12">
<a href="ac2k0201.htm">窗口接口使用简介<br>
</a></font></span><font color="#0000CC"><span class="p1"><font color="#0000CC"><img src="img/small.gif" width="12" height="12"></font>
<a href="ac2k0301.htm">用向导建立数据库</a></span></font><font color="#0000CC"><span class="p1"><a href="ac2k0301.htm">
<br>
</a><font color="#0000CC"><img src="img/small.gif" width="12" height="12"></font>
<a href="ac2k0401.htm">数据库的结构</a> <span class="p1"><a href="ac2k0403.htm">
</a></span> <br>
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用表向导建立表<br>
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<span class="p1"> <a href="ac2k0501.htm">表向导简介</a><br>
<a href="ac2k0502.htm">什么是字段、记录和值</a><br>
<a href="ac2k0503.htm">如何启动表向导</a><br>
<a href="ac2k0504.htm">怎样选择新表中的字段</a><br>
<a href="ac2k0505.htm">在表向导中修改字段名</a><br>
<a href="ac2k0506.htm">怎样在表中跳转</a><br>
补充内容 </span></span></font> <br>
<font color="#0000CC"><span class="p1"> </span></font><font color="#0000CC"><span class="p1"><a href="ac2k0501.htm">
<br>
</a><font color="#0000CC"><img src="img/small.gif" width="12" height="12"></font>
<a href="ac2k0601.htm">在表中输入数据<br>
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<a href="ac2k0701.htm">数据的类型和属性<br>
</a></span></font><span class="p1"><font color="#0000CC"><img src="img/small.gif" width="12" height="12"></font>
<a href="ac2k0801.htm" class="p1">定义表之间的关系<br>
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<a href="ac2k0901.htm">建立简单的查询</a><br>
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<a href="ac2k1001.htm">为查询制定规则</a><br>
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<a href="ac2k1101.htm">如何建立数据窗体<br>
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<a href="ac2k1201.htm">生成数据打印报表</a><br>
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<a href="ac2k1301.htm">为WEB页提供数据<br>
</a><font color="#0000CC"><img src="img/small.gif" width="12" height="12"></font>
<a href="ac2k1301.htm"></a></span><a href="ac2k1401.htm" class="p1">用图表显示数据</a><br>
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<a href="ac2k1301.htm"></a></span><a href="ac2k1501.htm"><span class="p1">宏的使用</span><br>
</a><span class="p1"><font color="#0000CC"><img src="img/small.gif" width="12" height="12"></font>
<a href="ac2k1301.htm"></a></span><a href="ac2k1601.htm"><span class="p1">模块与“VBA”语言</span><br>
</a><span class="p1"><font color="#0000CC"><img src="img/small.gif" width="12" height="12"></font>
<a href="ac2k1301.htm"></a></span><a href="ac2k1701.htm"><span class="p1">SQL语言妙用</span><br>
</a><span class="p1"><font color="#0000CC"><img src="img/small.gif" width="12" height="12"></font>
<a href="ac2k1301.htm"></a></span><a href="ac2k1801.htm"><span class="p1">外部数据的使用</span><br>
</a><span class="p1"><font color="#0000CC"><img src="img/small.gif" width="12" height="12"></font>
<a href="ac2k1301.htm"></a></span><a href="ac2k1901.htm"><span class="p1">数据的优化和安全</span><br>
</a><span class="p1"><font color="#0000CC"><img src="img/small.gif" width="12" height="12"></font>
<a href="ac2k1301.htm"></a></span><a href="ac2k2001.htm"><span class="p1">容易忽略的工作</span></a></p>
<p align="center" class=p1> <a href=/pc/bin/msg.pl?file_id=k_ac2k_5 target="_blank"><img src="/pc/img/message.gif" width="64" height="54" alt="请您留言" border="0"><br> 谈谈您的看法</a>
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<div align="center"><font color="#003333"><b><font color="#FF3333"><span style="line-height:17pt">什么是主键？</span></font></b></font></div>
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<td colspan="2" class="p2"><span style="line-height:17pt"> 在数据库中，常常不只是一个表，这些表之间也不是相互独立的。不同的表之间需要建立一种关系，才能将它们的数据相互沟通。而在这个沟通过程中，就需要表中有一个字段作为标志，不同的记录对应的字段取值不能相同，也不能是空白的。通过这个字段中不同的值可以区别各条记录。就像我们区别不同的人，每个人都有名字，但它却不能作为主键，因为人名很容易出现重复，而身份证号是每个人都不同的，所以可以根据它来区别不同的人。数据库的表中作为主键的字段就要像人的身份证号一样，必须是每个记录的值都不同，这样才能根据主键的值来确定不同的记录。
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