一、關於ADO
在基於ClIEnt/Server結構的數據庫環境中，通過OLE DB接口可以存取數據，但它定義的是低層COM接口，不僅不易使用，而且不能被VB，VBA，VBScript等高級編程工具訪問。
而使用ADO則可以很容易地使VB等編程語言直接訪問數據（通過OLE DB接口）。ADO是基於面向對象方法的，其對象模型如下圖所示(略)
由上圖可見，ADO對象模型總共才包括六個對象，相對於數據訪問對象（DAO）來說簡單得多。因此實際中常常使用它來訪問數據庫。
二、ADO訪問數據庫實例
下面，我們以Oracle為例，使用VB6.0來訪問其數據庫中的存儲過程。在此例中，我們首先在Oracle數據庫上創建有兩個存儲過程，一個不帶參數，另一個帶有參數。然後，使用ADO來訪問這兩個存儲過程。步驟如下：
1. 在Oracle服務器上運行以下DDL腳本:
DROP TABLE person;
CREATE TABLE person
(ssn NUMBER(9) PRIMARY KEY,
fname VARCHAR2(15),
lname VARCHAR2(20));
INSERT INTO person VALUES(555662222,'Sam','Goodwin');
INSERT INTO person VALUES(555882222,'Kent','Clark');
INSERT INTO person VALUES(666223333,'Jane','Doe');
COMMIT;
/
2. 在Oracle服務器上創建包（package）:
CREATE OR REPLACE PACKAGE packperson
AS
TYPE tssn is TABLE of NUMBER(10)
INDEX BY BINARY_INTEGER;
TYPE tfname is TABLE of VARCHAR2(15)
INDEX BY BINARY_INTEGER;
TYPE tlname is TABLE of VARCHAR2(20)
INDEX BY BINARY_INTEGER;
PROCEDURE allperson
(ssn OUT tssn,
fname OUT tfname,
lname OUT tlname);
PROCEDURE oneperson
(onessn IN NUMBER,
ssn OUT tssn,
fname OUT tfname,
lname OUT tlname);
END packperson;
/
3. 在Oracle服務器上創建以下包體（package body）：
CREATE OR REPLACE PACKAGE BODY packperson
AS
PROCEDURE allperson
(ssn OUT tssn,
fname OUT tfname,
lname OUT tlname)
IS
CURSOR person_cur IS
SELECT ssn, fname, lname
FROM person;
percount NUMBER DEFAULT 1;
BEGIN
FOR singleperson IN person_cur
LOOP
ssn(percount) := singleperson.ssn;
fname(percount) := singleperson.fname;
lname(percount) := singleperson.lname;
percount := percount + 1;
END LOOP;
END;
PROCEDURE oneperson
(onessn IN NUMBER,
ssn OUT tssn,
fname OUT tfname,
lname OUT tlname)
IS
CURSOR person_cur IS
SELECT ssn, fname, lname
FROM person
WHERE ssn = onessn;
percount NUMBER DEFAULT 1;
BEGIN
FOR singleperson IN person_cur
LOOP
ssn(percount) := singleperson.ssn;
fname(percount) := singleperson.fname;
lname(percount) := singleperson.lname;
percount := percount + 1;
END LOOP;
END;
END;
/
4. 在 VB 6.0 中打開一個新的工程，缺省創建表單 Form1。
5. 在表單上添加二個按鈕，cmdGetEveryone和cmdGetOne。
6. 在代碼窗口中添加以下代碼:
Option Explicit
Dim Cn As ADODB.Connection
Dim CPw1 As ADODB.Command
Dim CPw2 As ADODB.Command
Dim Rs As ADODB.Recordset
Dim Conn As String
Dim QSQL As String
Dim inputssn As Long
Private Sub cmdGetEveryone_Click()
Set Rs.Source = CPw1
Rs.Open
While Not Rs.EOF
MsgBox "Person data: " & Rs(0) & ",
" & Rs(1) & ", " & Rs(2)
Rs.MoveNext
Wend
Rs.Close
End Sub
Private Sub cmdGetOne_Click()
Set Rs.Source = CPw2
inputssn = InputBox(
"Enter the SSN you wish to retrIEve:")
CPw2(0) = inputssn
Rs.Open
MsgBox "Person data: " & Rs(0) & "
, " & Rs(1) & ", " & Rs(2)
Rs.Close
End Sub
Private Sub Form_Load()
'使用合適的值代替以下用戶ID，
口令（PWD）和服務器名稱（SERVER）
Conn = "UID=*****;PWD=*****;driver=" _
& "{Microsoft ODBC for
Oracle};SERVER=dSEOracle;"
Set Cn = New ADODB.Connection
'創建Connection對象
With Cn
.ConnectionString = Conn
.CursorLocation = adUseClIEnt
.Open
End With
QSQL = "{call packperson.allperson(
{resultset 9,ssn,fname,"_
& "lname})}"
Set CPw1 = New ADODB.Command
'創建Command對象
With CPw1
Set .ActiveConnection = Cn
.CommandText = QSQL
.CommandType = adCmdText
End With
QSQL ="{call packperson.oneperson(?,
{resultset 2,ssn, "_
& " fname,lname})}"
'調用存儲過程
Set CPw2 = New ADODB.Command
With CPw2
Set .ActiveConnection = Cn
.CommandText = QSQL
.CommandType = adCmdText
.Parameters.Append.CreateParameter(
,adInteger, _
adParamInput)
'添加存儲過程參數
End With
Set Rs = New ADODB.Recordset
With Rs
.CursorType = adOpenStatic
.LockType = adLockReadOnly
End With
End Sub
Private Sub Form_Unload(Cancel As Integer)
Cn.Close
Set Cn = Nothing
Set CPw1 = Nothing
Set CPw2 = Nothing
Set Rs = Nothing
End Sub
7. 運行程序。當點下cmdGetEveryone按鈕時，程序調用Oracle數據庫中不帶參數的存儲過程packperson.allperson，點下cmdGetOne按鈕時調用packperson.oneperson存儲過程。
