mysql - 如何检测 vb.net 和 mysql 数据库中的重复条目

Question

我在 vb.net 和使用 mysql 数据库中遇到问题。我已经有一个保存按钮代码，但我的问题是我需要检测重复的数据。我尝试搜索它，但它不适用于我的代码，总是出现错误或警告。我的问题是通过这段代码，我在哪里放置代码来检测重复条目？

con = New MySqlConnection
con.ConnectionString = "server = localhost; database=db; uid=root;pwd="
Dim reader As MySqlDataReader
Try
    con.Open()
    Dim query As String
    query = "insert into paraiso_dbms2.client_t(FIRSTNAME,MIDDLENAME,LASTNAME,GENDER,BIRTHDATE,AGE,STREET,BARANGAY,CITY,ZIPCODE,PHONE_NUMBER) VALUES('" & txtfirstname.Text & "','" & txtmidname.Text & "','" & txtlastn.Text & "','" & gender & "','" & dpbd.Text & "','" & txtage.Text & "','" & txtstreet.Text & "','" & txtbrgy.Text & "','" & txtcity.Text & "','" & txtzipcode.Text & "','" & txtphone.Text & "')"
    cmd = New MySqlCommand(query, con)
    reader = cmd.ExecuteReader
    MessageBox.Show("Saved Sucessfully!")
    con.Close()
Catch ex As Exception
    MessageBox.Show(ex.Message)
Finally
    con.Dispose()
End Try
load_table()

Answer 1

您应该更新当前的插入代码如下

con = New MySqlConnection
con.ConnectionString = "server = localhost; database=db; uid=root;pwd="
Try
    con.Open()
    Dim query As String
    query = "insert into paraiso_dbms2.client_t(FIRSTNAME,MIDDLENAME,LASTNAME,GENDER,BIRTHDATE,AGE,STREET,BARANGAY,CITY,ZIPCODE,PHONE_NUMBER) VALUES('" & txtfirstname.Text & "','" & txtmidname.Text & "','" & txtlastn.Text & "','" & gender & "','" & dpbd.Text & "','" & txtage.Text & "','" & txtstreet.Text & "','" & txtbrgy.Text & "','" & txtcity.Text & "','" & txtzipcode.Text & "','" & txtphone.Text & "')"
    cmd = New MySqlCommand(query, con)
    reader = cmd.ExecuteNonQuery
    MessageBox.Show("Saved Sucessfully!")
    con.Close()
Catch ex As Exception
    MessageBox.Show(ex.Message)
Finally
    con.Dispose()
End Try
load_table()

以及如何检查记录是否存在，您可以将电话号码与电话号码文本框进行比较，因为没有唯一的号码或电子邮件

con = New MySqlConnection
con.ConnectionString = "server = localhost; database=db; uid=root;pwd="
Try
    con.Open()
    Dim query As String
    query = "select PHONE_NUMBER from paraiso_dbms2.client_t where PHONE_NUMBER='" & txtphone.Text & "'"
    cmd = New MySqlCommand(query, con)
   dim count as string = cmd.ExecuteScalar
    MessageBox.Show(count)
    con.Close()
Catch ex As Exception
    MessageBox.Show(ex.Message)
Finally
    con.Dispose()
End Try

即使我不确定这是否适合你，因为我没有看到整个代码，如果没有的话我会给你新的