如何用VB连接SQL数据库做登录
一、界面设计
各控件名称属性分别为:label1 、text1 、label2、text2、commandok、cmdcancel
登录成功后显示的窗体:
代码设计如下:
'首先添加一个模块,写上以下通用声明和Sub main():
Public conn As ADODB.Connection '通用(声明)
Sub main()
Set conn = New ADODB.Connection '通用(main)
conn.ConnectionString = "Provider=SQLOLEDB.1;Persist Security Info=False;" _
+ "User ID=sa;password=123;Initial Catalog=denglu;Data Source=127.0.0.1" '连接数据库代码
conn.Open
frmLogin.Show '首先显示登录界面。也可以在工程属性中设置启动对象为Sub main()或者frmlogin窗体
End Sub
'在Frmlogin 代码窗口,为cmdok控件写以下代码:
Private Sub cmdok_Click()
If text1.Text = "" Then
MsgBox "用户名不能为空!", vbOKOnly + vbInformation, "友情提示"
text1.SetFocus
Exit Sub '若用户名文本框内为空,则出现提示框
End If
If text2.Text = "" Then
MsgBox "密码不能为空!", vbOKOnly + vbInformation, "友情提示"
text2.SetFocus
Exit Sub '若输入密码文本框为空,也出现提示框
End If
Dim strSQl As String
strSQl = "select * from User1 where username='" & Trim$(text1.Text) & "' and pwd='" & Trim$(text2.Text) & "' "
'书写SQL代码,查询User1表中是否存在窗体中用户输入的信息。
Dim str As New ADODB.Recordset
Set str = New ADODB.Recordset
str.CursorLocation = adUseClient
str.Open strSQl, conn, adOpenStatic, adLockReadOnly
With str
If .State = adStateOpen Then .Close
.Open strSQl
If .EOF Then
Try_times = Try_times + 1
If Try_times >= 3 Then
MsgBox "您已连续三次输入错误,系统将自动关闭", vbOKOnly + vbCritical, "警告"
Unload Me '若用户连续输入3次错误密码,则系统关闭
Else
MsgBox "对不起,用户名不存在或密码错误 !", vbOKOnly + vbQuestion, "警告"
text1.SetFocus
text1.Text = ""
text2.Text = ""
End If
Else
Unload Me '若登录成功,则隐藏当前窗体
Form2.Show '然后显示Form窗体
End If
End With
End Sub
Private Sub cmdCancel_Click()
End '若单击Cmdcel按钮,则结束应用程序
End Sub
运行中存在的问题:
代码中有Dim conn As adodb.connection,运行时显示"用户定义类型未定义"
解决方法:点击“工程”--“引用”找到“Microsoft ActiveX Data Object 2.6”
然后就就可以正常运行了。
2015-02-14 · 知道合伙人数码行家
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,然后将以上代码复制,OK搞定
4) 以上方式无需加载ADO控件,方便!