Question

vb.net sql数据库 判断某字段的值是否重复

Dim CELL As String = ("select count(*) from LC215DT9A02 where CELL条码='" & TextBox1.Text & "'")
Dim myCommandCell As New SqlCommand(CELL, Conn)
Conn.Open()
Dim myReaderCell As SqlDataReader
myReaderCell = myCommandCell.ExecuteReader()
If myReaderCell.Read() Then
MsgBox("CELL条码已存在，请重新输入")
Call 清空()
Exit Sub
Else
Call 添加()
End If
Conn.Close()

怎么判断如果CELL条码字段中已存在数据就显示MsgBox内容，不存在就添加
我上面这样写不管有没有重复都出现MsgBox

Answer 1

Dim CELL As String = ("select count(*) from LC215DT9A02 where CELL条码='" & TextBox1.Text & "'")
Dim myCommandCell As New SqlCommand(CELL, Conn)
Conn.Open()

If myCommandCell .ExecuteScalar() Then
MsgBox("CELL条码已存在，请重新输入")
Call 清空()
Exit Sub
Else
Call 添加()
End If
Conn.Close()

这样改试一下。