Question

vb如何查询数据库记录是否存在

我用的是adodc控件
Ado3.RecordSource = "select * from 借出记录 where 编号='" + Text1.Text + "'"
If Text1.Text = "" Then
Text4.Text = ""
Text2.Text = ""
Text5.Text = ""
Text6.Text = ""
Text7.Text = ""
Chk1.Value = 0
Else
Ado3.Refresh
Text4.Text = Ado3.Recordset.Fields("名称")
Text2.Text = Ado3.Recordset.Fields("读者编号")
Text5.Text = Ado3.Recordset.Fields("条形码")
Text6.Text = Ado3.Recordset.Fields("应还日期")
Text7.Text = Ado3.Recordset.Fields("押金")
End If

当点击按钮后实行查询，并把字段数据输出到文本框中，但如果记录不存在则会出错，请问该如何补充？

Answer 1

Ado3.RecordSource = "select * from 借出记录 where 编号='" + Text1.Text + "'"
Ado3.Refresh
if rs.eof = true then
Text4.Text = Ado3.Recordset.Fields("名称")
Text2.Text = Ado3.Recordset.Fields("读者编号")
Text5.Text = Ado3.Recordset.Fields("条形码")
Text6.Text = Ado3.Recordset.Fields("应还日期")
Text7.Text = Ado3.Recordset.Fields("押金")
else
Text4.Text = ""
Text2.Text = ""
Text5.Text = ""
Text6.Text = ""
Text7.Text = ""
Chk1.Value = 0
Else
End If

Answer 2

Ado3.RecordSource = "select * from 借出记录 where 编号='" + Text1.Text + "'"
if not rs.eof then
If Text1.Text = "" Then
Text4.Text = ""
Text2.Text = ""
Text5.Text = ""
Text6.Text = ""
Text7.Text = ""
Chk1.Value = 0
Else
Ado3.Refresh
Text4.Text = Ado3.Recordset.Fields("名称")
Text2.Text = Ado3.Recordset.Fields("读者编号")
Text5.Text = Ado3.Recordset.Fields("条形码")
Text6.Text = Ado3.Recordset.Fields("应还日期")
Text7.Text = Ado3.Recordset.Fields("押金")
End If
else
response.write "没有该记录！"
end if

Answer 3

Ado3.RecordSource = "select * from 借出记录 where 编号='" + Text1.Text + "'"
If Text1.Text = "" Then
Text4.Text = ""
Text2.Text = ""
Text5.Text = ""
Text6.Text = ""
Text7.Text = ""
Chk1.Value = 0
Else
Ado3.Refresh
If Not Ado3.Recordset.EOF Then
Text4.Text = Ado3.Recordset.Fields("名称")
Text2.Text = Ado3.Recordset.Fields("读者编号")
Text5.Text = Ado3.Recordset.Fields("条形码")
Text6.Text = Ado3.Recordset.Fields("应还日期")
Text7.Text = Ado3.Recordset.Fields("押金")
Else
MsgBox"记录不存在！"
End If
End If

Answer 4

Ado3.RecordSource = "select * from 借出记录 where 编号='" + Text1.Text + "'"
If Text1.Text = "" Then
Text4.Text = ""
Text2.Text = ""
Text5.Text = ""
Text6.Text = ""
Text7.Text = ""
Chk1.Value = 0
Else
Ado3.Refresh
if not ado3.recordset.eof then
Text4.Text = Ado3.Recordset.Fields("名称")
Text2.Text = Ado3.Recordset.Fields("读者编号")
Text5.Text = Ado3.Recordset.Fields("条形码")
Text6.Text = Ado3.Recordset.Fields("应还日期")
Text7.Text = Ado3.Recordset.Fields("押金")
end if
End If

Answer 5

加个条件
Ado3.Recordset.recordcount>0