采用DAO方式访问数据库,如何监测数据库中是否存在某个表,如果没有则生成?

2006-06-25 09:46:33 118 阅读 AI 写同款 · GEO 优化AI 选题数据监测一键分发 ›

uniapp+openlayers集成天地图实战：renderjs通信陷阱与性能优化避坑指南本文深入探讨了uniapp与openlayers集成天地图时的renderjs通信陷阱与性能优化策略。通过实战案例解析了renderjs的特殊通信机制、地图实例生命周期管理、图层懒加载等关键技巧，帮助开发者避免常见坑点，提升应用流畅度。特别针对多语言切换、热重载偏移等疑难问题提供了解决方案，是uniapp+openlayers开发者的实用避坑指南。阅读详情

我的程序由于需要考虑和以前的版本相兼容,想在数据库中增加一个表实现新的功能.但是原来的数据库中,没有这个表,想实现如题目的功能.该如何判断,谢谢

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使用RepeatModeler和RepeatMasker注释基因组重复序列重复序列注释有两种常用策略，基于同源序列相似性和基于重复序列结构特征。RepeatMasker是基于同源序列相似性注释序列的常用工具, RepeatModeler可用来从头对基因组的重复序列家族进行建模注释，它的核心组件是RECON和RepatScout。这篇教程介绍如何使用RepeatModeler从头鉴定基因组的重复序列，之后用RepeatMasker根据自... 阅读详情

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syy64 2006-06-26

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BOOL CDlgTest::CreateAccessTable()
{
_bstr_t strSQL;
CString strTemSQL;
CString str, str1, str2, str3;
CString strTabName,strName;

CStringArray stt;
CStringArray stTabName;

int i,n;
HRESULT hr(-1);

UpdateData(TRUE);
//OnSelchangeComboType();

n=m_List.GetItemCount();
stt.SetSize(n);
for (i=0;i<n;i++)
{
if(m_List.GetItemText(i,1)=="Text")
{
strTemSQL=m_List.GetItemText(i,0) + " " +
m_List.GetItemText(i,1) + "(" +
m_List.GetItemText(i,2) + ")" + ",";

}
else if (m_List.GetItemText(i,1)=="Autoincremnet")
{
strTemSQL=m_List.GetItemText(i,0) + " " +
m_List.GetItemText(i,1) + ",";
}
else if (m_List.GetItemText(i,1)=="Currency")
{
strTemSQL=m_List.GetItemText(i,0) + " " +
m_List.GetItemText(i,1) + ",";

}
else if(m_List.GetItemText(i,1)=="DateTime")
{
strTemSQL=m_List.GetItemText(i,0) + " " +
m_List.GetItemText(i,1) + ",";
}
else if(m_List.GetItemText(i,1)=="Text")
{
strTemSQL=m_List.GetItemText(i,0) + " " +
m_List.GetItemText(i,1) + "(" +
m_List.GetItemText(i,2) + ")" + ",";
}
else if(m_List.GetItemText(i,1)=="Double")
{
strTemSQL=m_List.GetItemText(i,0) + " " +
m_List.GetItemText(i,1) + ",";
}
else if(m_List.GetItemText(i,1)=="Decimal")
{
strTemSQL=m_List.GetItemText(i,0) + " " +
m_List.GetItemText(i,1) + "(" +
m_List.GetItemText(i,2) + "," +
m_List.GetItemText(i,3) + ")" + ",";
}
else if(m_List.GetItemText(i,1)=="Single")
{
strTemSQL=m_List.GetItemText(i,0) + " " +
m_List.GetItemText(i,1) + ",";
}
else if(m_List.GetItemText(i,1)=="Integer")
{
strTemSQL=m_List.GetItemText(i,0) + " " +
m_List.GetItemText(i,1) + ",";

}
/* else if (m_List.GetItemText(i,1)=="Yes")
{
strTemSQL=m_List.GetItemText(i,0) + " " +
m_List.GetItemText(i,1) + ",";
}*/
stt[i] = strTemSQL;

}
str2 = m_List.GetItemText(0,0);
str3 = "";
for(i=0;i<n;i++)
{
if(ListView_GetCheckState(m_List,i))
{

if(i>0)
{
str1 = m_List.GetItemText(i,0);

str.Format("%s,%s",str2,str1);
str2 = str;
}
str.Format("%s%s",str3,stt[i]);
str3 = str;
}
}

// BOOL bOpenFileDialog= false;
// CString filepath;
// CString m_strResult;
// CString strName;
// LPCTSTR lpszDefExt = _T("");
// LPCTSTR lpszFileName= _T("tabAccess");
// //DWORD dwFlags = OFN_HIDEREADONLY;
// DWORD dwFlags = OFN_OVERWRITEPROMPT;
//
//
// LPCTSTR lpszFilter = _T("(*.*)|*.*|");
//
// CFileDialog dlg(bOpenFileDialog,
// lpszDefExt,lpszFileName,
// dwFlags,lpszFilter,CWnd::FromHandle(hMainWnd));
// dlg.m_ofn.lpstrTitle = _T("Êý¾Ý¿âÎÄ¼þ");
// if(dlg.DoModal()==IDOK)
// {
// filepath=dlg.GetPathName();
// strName=dlg.GetFileName();
//
// UpdateData(FALSE);
// }
try
{
m_pRecordset=theApp.m_pConnection->OpenSchema(adSchemaTables);
while(!(m_pRecordset->adoEOF))
{
//»ñÈ¡±í¸ñ
_bstr_t table_name = m_pRecordset->Fields->GetItem("TABLE_NAME")->Value;
//»ñÈ¡±í¸ñÀàÐÍ
_bstr_t table_type = m_pRecordset->Fields->GetItem("TABLE_TYPE")->Value;

//¹ýÂËÒ»ÏÂ£¬Ö»Êä³ö±í¸ñÃû³Æ£¬ÆäËûµÄÊ¡ÂÔ

if ( strcmp(((LPCSTR)table_type),"TABLE")==0)
{
strTabName=(LPCSTR)table_name;
if(m_strTabName=="")
{
::MessageBox(NULL,"±íÃû²»ÄÜÎª¿Õ,ÇëÊäÈë±íÃû","ÌáÊ¾",MB_OK);

return false;
}

else if(strTabName==m_strTabName)
{
strName.Format("±íÃû%sÒÑ¾´æÔÚ,ÇëÖØÐÂÊäÈë!",m_strTabName);
::MessageBox(NULL,strName,"ÌáÊ¾",MB_OK);
return false;
}

}
m_pRecordset->MoveNext();
}

strName=m_strTabName;
}
catch(_com_error e)///²¶×½Òì³£
{
::MessageBox(NULL,e.Description(),"ÌáÊ¾",MB_OK);
return FALSE;
}

str.Format("CREATE TABLE %s (ID INTEGER,X decimal(10,2),Y decimal(10,2),Z decimal(10,2),%s CONSTRAINT MyTableConstraint PRIMARY KEY(ID),UNIQUE(X,Y,Z,%s))", strName,str3, str2);
// str = "CREATE TABLE tabAccess (ID INTEGER,X F(10,2),Y F(10,2),Z F(10,2), CONSTRAINT MyTableConstraint PRIMARY KEY(ID), UNIQUE(X,Y,Z))";
// str = "CREATE TABLE %s (ID INTEGER,X Number,Y Double,Z Double, CONSTRAINT MyTableConstraint PRIMARY KEY(ID), UNIQUE(X,Y,Z))";

strSQL= str;
try
{

theApp.m_pConnection->Execute(strSQL,NULL,adCmdText);
//theApp.m_pConnection->Execute(strTemSQL,NULL,adCmdText);

}
// hr = (HRESULT)0;
catch (_com_error &e)
{
::MessageBox(NULL,e.Description(),"ÌáÊ¾",MB_OK);

//hr = e.WCodeToHRESULT(e.WCode());

return FALSE;
}

//::MessageBox(NULL,"´´½¨±í³É¹¦£¡","ÌáÊ¾",MB_OK);
UINT j=::MessageBox(NULL,"´´½¨±í³É¹¦£¡","ÌáÊ¾",MB_OK);;
if(j==IDOK)
{
UINT i=::MessageBox(NULL,"ÊÇ·ñÏÖÔÚ²é¿´±í½á¹¹","ÌáÊ¾",MB_YESNO);
if(i==IDYES)
{
UpdateData(true);
CString str="";
/* int ncount=rstab.m_cmbTable.GetCount();
for(int num=0;num<ncount;num++)
{
rstab.m_cmbTable.GetLBText(num,m_strTabName);
}*/
CDlgRecordset dlg(this);
dlg.m_strCMBTable = m_strTabName;
/* int ncount=dlg.m_cmbTable.GetCount();
for(int num=0;num<ncount;num++)
{
dlg.m_cmbTable.GetLBText(num,str);
if(str==m_strTabName)
{
str=m_strTabName;
break;
}
}*/
/// dlg.m_cmbTable.SetCurSel(num);
dlg.DoModal();
}
else
{
CDlgTest dlg(this);
dlg.DoModal();
}
}
return TRUE;

}

gezihou 2006-06-26

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查一查数据库的系统表里面应该有已存在表的信息

采用DAO方式访问数据库,如何监测数据库中是否存在某个表,如果没有则生成?

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