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cellspacing="1" cellpadding="1" bgcolor="#000000"><tr bgcolor="#FFFFFF"><td width="100%" colspan="4" align="left"><table width="95%" align="center"><tr><td class="font1"><p align="center"><br><font size="3">用Delphi 开发数据库程序经验三则</font><br><span class="nava"><font color="#CC9933">2000-06-10· -·中国计算机报社</font></span></p><strong>1.建立临时表<br> </strong> 数据输入是开发数据库程序的必然环节。在Client/Server结构中，客户端可能要输入一批数据后，再向服务器的后台数据库提交，这就需要在本地（客户端）建立临时数据表来存储用户输入的数据，待提交后，清除本地表数据。这种方法的好处是：提高输入效率，减小网络负担。<br> <br> 由于用户一次输入的数据量一般情况下较小（不会超过几百条记录），所以临时表可以建立在内存中，这样处理速度较快。<br> <strong>方法1：使用查询控件(TQuery)</strong><br> 第1步：在窗体上放上查询控件(TQuery)，设置好所连接的数据表。<br> 第2步：使TQuery. CachedUpdates=True;<br> TQuery. RequestLive=True<br> 第3步：在原有的SQL语句后加入一条Where子语句，要求加入这条Where子语句后SQL查询结果为空。<br> 例如：<br> SELECT Biolife.″Species No″, Category, Common_Name, Biolife.″Species Name″, Biolife.″Length (cm)″, Length_In, Notes, Graphic<br> FROM ″biolife.db″ Biolife<br> where Biolife.Category=′A′ and Biolife.Category=′B′<br> 这样临时表就建立完成了。<br> <br> <strong>方法2：使用代码创建临时表</strong><br> 代码如下：<br> function CreateTableInMemory(const AFieldDefs:TFieldDefs):TDataSet;<br> var <br> TempTable:TClientDataSet;<br> begin<br> TempTable:=nil;<br> Result:=nil;<br> if AFieldDefs<>nil then<br> begin<br> try<br> TempTable:=TClientDataSet.Create(Application);<br> TempTable.FieldDefs.Assign(AFieldDefs);<br> TempTable.CreateDataSet;<br> Result:=(TempTable as TDataSet);<br> Except<br> if TempTable<>nil then <br> TempTable.Free;<br> <br> Result:=nil;<br> raise;<br> end<br> end<br> end;<br> <br> 在程序中按如下方法使用：<br> procedure TForm1.Button1Click(Sender: TObject);<br> var <br> ADataSet:TDataSet;<br> begin<br>⌨️ 快捷键说明
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