Question

VB设置注册用户要判断在ACCESS里面用户是否已存在，该在哪里添加那些代码？

数据库log.mdb，表名login，表里用户保存列名username，密码保存列名password。
注册窗体Command1_Click()代码如下：
Private Sub Command1_Click()
centerform Me
If Text1 = "" Then
MsgBox "请输入账号!", vbCritical, "错误"
Else
If Text1 <> "" And Text2 = "" Or Text3 = "" Then
MsgBox "请输入密码!", vbCritical, "错误"
Else
If Text2.Text <> Text3.Text Then
MsgBox "两次输入密码不一致!", vbCritical, "错误"
Else
If Text2.Text = Text3.Text Then
Dim conn As ADODB.Connection
Dim rs As New ADODB.Recordset
Dim sql As String
Set conn = CreateObject("adodb.connection")
conn.Open "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & App.Path & "\log.mdb "
sql = "select * from login"
rs.CursorLocation = adUseClient
rs.Open sql, conn, adOpenKeyset, adLockPessimistic
rs.AddNew
rs.Fields("username").Value = Text1.Text
rs.Fields("password").Value = Text2.Text
rs.Update
rs.Close
conn.Close
MsgBox "注册成功，返回登陆界面!", vbExclamation, "提示"
Form1.Show
Unload Me
End If
End If
End If
End If
End Sub

Answer 1

只要写在连接数据库后，注册前就行吧
Dim conn As ADODB.Connection
Dim rs As New ADODB.Recordset
Dim sql As String
Set conn = CreateObject("adodb.connection")
conn.Open "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & App.Path & "\log.mdb "
——————————————————————————————————————————
rs.Open "SELECT * FROM login where username='" & Text1 & "'", conn, adOpenKeyset, adLockOptimistic
If rs.RecordCount > 0 Then
MsgBox "用户名已存在!", vbCritical, "错误"
rs.Close
Exit Sub
End If
rs.Close
——————————————————————————————————————————
sql = "select * from login"
rs.CursorLocation = adUseClient
rs.Open sql, conn, adOpenKeyset, adLockPessimistic
rs.AddNew
rs.Fields("username").Value = Text1.Text
rs.Fields("password").Value = Text2.Text
rs.Update
rs.Close
conn.Close
MsgBox "注册成功，返回登陆界面!", vbExclamation, "提示"
Form1.Show