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.
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;"
IV)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RDS方式）：
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=;"