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=somepathmydb.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=somepathmydb.mdb;" & _
            "Uid=Admin;" & _
            "Pwd=;"
    ii)如果使用了System database:
        oConn.Open _
            "Driver={Microsoft Access Driver (*.mdb)};" & _
            "Dbq=somepathmydb.mdb;" & _
            "SystemDB=somepathmydb.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