下面将简单介绍一下几种ADO连接方式：ODBC DSN,ODBC DSN-Less,
OLE DB Provider,和"MS Remote" Provider.
1。ODBC DSN连接
I.DSN
 oConn.Open "DSN=AdvWorks;" & _
  "UID=Admin;" & _
  "PWD=;"
注意：从MDAC2.1开始就不能够在使用这样的方式了，就是只把DSN文件名放在ConnectString中
你必须同时使用DSN，UID，PWD标志。例如下面的方式在MDAC 2.1中将会出错：
 oConn.Open "AdvWorks"



II.File DSN
 oConn.Open "FILEDSN=\somepath\mydb.dsn;" & _
  "UID=Admin;" & _
  "PWD=;"
III.ODBC DSN-Less Connections
a)ODBC Text Driver
 oConn.Open _
  "Driver={Microsoft Text Driver (*.txt; *.csv)};" & _
  "Dbq=\somepath\;" & _
  "Extensions=asc,csv,tab,txt;" & _
  "Persist Security Info=False"
注意：需要在SQL语句中指定使用到的文件名。例如：
 oRs.Open "Select * From customer.csv", _
  oConn, adOpenStatic, adLockReadOnly, adCmdText
b)ODBC Driver for Access
 i)普通安全模式：
  oConn.Open _
"Driver={Microsoft Access Driver (*.mdb)};" & _
"Dbq=\somepath\mydb.mdb;" & _
"Uid=Admin;" & _
"Pwd=;"
 ii)如果使用了System database:
  oConn.Open _
"Driver={Microsoft Access Driver (*.mdb)};" & _
"Dbq=\somepath\mydb.mdb;" & _
"SystemDB=\somepath\mydb.mdw;", _
"admin", ""
c)ODBC Driver for SQL Server
 i)普通安全模式
  oConn.Open "Driver={SQL Server};" & _
"Server=carl2;" & _
"Database=pubs;" & _
"Uid=sa;" & _
"Pwd=;"
 ii)使用信任安全模式：
  oConn.Open "Driver={SQL Server};" & _
"Server=carl2;" & _
"Database=pubs;" & _
"Uid=;" & _
"Pwd=;"
 注意：要使用空白的Uid和Pwd 
d)ODBC Driver for Oracle
 i)使用现有的Oracle ODBC Driver from Microsoft:
  oConn.Open _
"Driver={Microsoft ODBC for Oracle};" & _
"Server=OracleServer.world;" & _
"Uid=demo;" & _
"Pwd=demo;"
 ii)使用老版本的Oracle ODBC Driver from Microsoft:
  oConn.Open _
"Driver={Microsoft ODBC Driver for Oracle};" & _
"ConnectString=OracleServer.world;" & _
"Uid=demo;" & _
"Pwd=demo;"
IIII)使用微软的OLE DB Data Link Connections方式Data Link File (UDL)
a)使用绝对路径
 oConn.Open "File Name=\somepath\pubs.udl;"
b)使用相对路径
 oConn.Open "File Name=pubs.udl;"
V)OLE DB Provider Connections方式
a)OLE DB Provider for ODBC Databases
 i)Access (Jet):
  oConn.Open _
"Provider=MSDASQL;" & _
"Driver={Microsoft Access Driver (*.mdb)};" & _
"Dbq=\somepath\mydb.mdb;" & _
"Uid=Admin;" & _
"Pwd=;"
 ii)SQL Server:
  oConn.Open _
"Provider=MSDASQL;" & _  
"Driver={SQL Server};" & _
"Server=carl2;" & _
"Database=pubs;" & _
"Uid=sa;" & _
"Pwd=;"
b)OLE DB Provider for Microsoft Jet  (Access)
 i)普通安全模式：
  oConn.Open _
"Provider=Microsoft.Jet.OLEDB.4.0;" & _
"Data Source=\somepath\mydb.mdb;" & _
"User Id=admin;" & _
"Password=;"
 ii)如果使用了System database:
  oConn.Open _
"Provider=Microsoft.Jet.OLEDB.4.0;" & _
"Data Source=\somepath\mydb.mdb;" & _
"Jet OLEDB:System Database=system.mdw;", _
"admin", ""
 注意：当使用OLE DB Provider4.0版本是，需要把MDB和MDW文件转换成4.0的数据库格式
 iii)如果MDB需要一个数据库密码的话：
  oConn.Open _
"Provider=Microsoft.Jet.OLEDB.4.0;" & _
"Data Source=\somepath\mydb.mdb;" & _
"Jet OLEDB:Database Password=MyDbPassword;", _
"admin", ""
c)OLE DB Provider for Excel Spreadsheet:
  oConn.Open _
"Provider=Microsoft.Jet.OLEDB.4.0;" & _
"Data Source=\somepath\expenses.xls;" & _
"Extended Properties=""Excel 8.0;HDR=Yes;"";"
 注意： "HDR=Yes"表示在第一行中是行标题，在provider中将不把第一行包括入recordset中
d)OLE DB Provider for SQL Server
 i)普通安全模式：
  oConn.Open "Provider=sqloledb;" & _
"Network Library=DBMSSOCN;" & _
"Data Source=carl2;" & _
"Initial Catalog=pubs;" & _
"User Id=sa;" & _
"Password=;"
 ii)使用信任安全模式：
  oConn.Open "Provider=sqloledb;" & _
Network Library=DBMSSOCN;" & _
"Data Source=carl2;" & _
"Initial Catalog=pubs;" & _
"Trusted_Connection=yes;"
 注意："Network Library=DBMSSOCN"声明OLE DB使用TCP/IP替代Named Pipes.
e)OLE DB Provider for Oracle
 oConn.Open "Provider=msdaora;" & _
  "Data Source=OracleServer.world;" & _
  "User Id=sa;" & _
  "Password=;"
(VI)Remote OLE DB Provider Connections方式（就是我一直在研究的RDS方式哦，呵呵。）：
a)MS Remote - Access (Jet)
 i)ODBC DSN:
  oConn.Open "Remote Server=http://carl2;" & _
"Remote Provider=MSDASQL;" & _
"DSN=AdvWorks;" & _
"Uid=admin" & _
"Pwd=;"
 ii)OLE DB Provider:
  oConn.Open "Provider=MS Remote;" & _
"Remote Server=http://carl2;" & _
"Remote Provider=Microsoft.Jet.OLEDB.4.0;" & _
"Data Source=\somepath\mydb.mdb;", _
"admin", ""
 iii)OLE DB Provider自定义事务对象
  oConn.Open "Provider=MS Remote;" & _
"Remote Server=http://carl2;" & _
"Handler=MSDFMAP.Handler;" & _
"Data Source=MyAdvworksOLEDBConnectTag;"
b)MS Remote - SQL Server
 i)ODBC DSN:
  oConn.Open "Remote Server=http://carl2;" & _
"Remote Provider=MSDASQL;" & _
"Network Library=DBMSSOCN;" & _
"DSN=Pubs;" & _
"Uid=sa" & _
"Pwd=;"
 ii)OLE DB Provider
  oConn.Open "Provider=MS Remote;" & _
"Remote Server=http://carl2;" & _
"Remote Provider=SQLOLEDB;" & _
"Network Library=DBMSSOCN;" & _
"Data Source=carl2;" & _
"Initial Catalog=pubs;" & _
"User ID=sa;" & _
"Password=;"