Question

如何用VB连接SQL数据库做登录

Answer 1

VB使用ADO数据库可以分为有源数据库和无源数据库，即是否使用了DSN数据源，如下例：
1、在连接数据库前首先要在VB菜单中“工程”-“引用”从中选择 microsoft activeX Data objects 2.6 library和 microsoft activeX Data objects recordset 2.6两个组件，这是在连接数据前所必做的工作。
2、接下来定义ADO的连接对象，如下所示：
Set conn = New ADODB.Connection
Set rs = New ADODB.Recordset
第一种方法采用的是无源的数据库连接方法
conn.ConnectionString = "Driver={sql server};server=JSZX3-11;uid=sa;pwd=;database=wzc"
conn.ConnectionTimeout = 30
conn.Open
rs.Open "select 用户名,密码 from login where 用户名='" & Trim(Combo1.Text) & "' And 密码='" & Trim(Text1.Text) & "'", conn, adOpenStatic, adLockReadOnly, adCmdText
If rs.EOF = True And rs.BOF Then
m = MsgBox("请重新登录", vbExclamation)
Text1.Text = ""
Text1.SetFocus
Else
Form1.Hide
End If
rs.Close
这是第二种方法连接数据库的方法，这一种方法是采用有源的方法与数据库连接的方法，代码如下所示：
Set conn = New ADODB.Connection
Set rs = New ADODB.Recordset
conn.ConnectionString = "DSN=login;uid=sa;pwd=;"
conn.ConnectionTimeout = 30
conn.Open
rs.Open "select 用户名 from login", conn, adOpenStatic, adLockReadOnly, adCmdText
Dim i As String
For t = 0 To Val(rs.RecordCount) - 1
i = Trim(rs.Fields("用户名").Value)
rs.MoveNext
Combo1.AddItem i
Next t
rs.Close

Answer 2

Option Explicit
Private Function Selectsql(SQL As String) As ADODB.Recordset '返回ADODB.Recordset对象
Dim ConnStr As String
Dim Conn As ADODB.Connection
Dim rs As ADODB.Recordset
Set rs = New ADODB.Recordset
Set Conn = New ADODB.Connection

'On Error GoTo MyErr:
ConnStr = "Provider=SQLOLEDB.1;Persist Security Info=True;User ID=登录数据库用户名(默认为sa);Password=登录数据库密码;Initial Catalog=数据库名;Data Source=服务器名(默认为:MERRYCHINA)" '这是连接SQL数据库的语句
Conn.Open ConnStr
rs.CursorLocation = adUseClient
rs.Open Trim$(SQL), Conn, adOpenDynamic, adLockOptimistic
Set Selectsql = rs
'Exit Function
'MyErr:
'Set rs = Nothing
'Set Conn = Nothing '释放相关的系统资源
'MsgBox Err.Description, vbInformation, "系统提示" '显示出错信息
End Function
Private Sub Form_Load()
Dim SQL As String
Dim rs As ADODB.Recordset
Dim X As Long
On Error GoTo Err_box
SQL = " select * from 用户表"
Set rs = Selectsql(SQL)
If rs.RecordCount > 0 Then
rs.MoveFirst
For X = 1 To rs.RecordCount
Combo1.AddItem rs.Fields("用户名").Value
rs.MoveNext
Next X
Combo1.ListIndex = 0
End If
rs.Close
Exit Sub
Err_box:
End Sub
Private Sub Command1_Click()
Dim SQL As String
Dim rs As ADODB.Recordset
If Text1.Text = "" Then
MsgBox "请输入口令!", 16
Text1.SetFocus
Exit Sub
End If
If Combo1.Text = "" Then
MsgBox "请选择登录用户!", 16
Combo1.SetFocus
Exit Sub
End If
SQL = "SELECT * FROM 用户表 WHERE 用户名='" & Combo1.Text & "' AND 密码='" & Text1.Text & "' "
Set rs = Selectsql(SQL)
If rs.RecordCount > 0 Then
Form1.Show '想要打开的主窗体
MsgBox "恭喜兄弟,登录成功!", 64, "提示"
Unload Me
Else
MsgBox "口令不对,请重新输入!", 16, "提示"
Text1.SetFocus
End If
End Sub
'**********************************************************************
'说明:1) 在工程中引用Microsoft ActiveX Data Objects 2.8 Library ,其它版本也行如:2.0
' 2) 在窗体中加Texe1.text(文本框控件),Combo1.text(组合框控件),Command1(命令按钮)各一个
' 3) 在SQL Server2000中创建数据库，新建表"用户表",表中包含"ID,姓名,密码"等字段,