更新查询使数据库中的字段为空

Question

我之前问过一个关于使用 phpMyAdmin 在 datagridview 中更新数据的问题。您可以通过以下链接参考它-->Updating data in phpmyadmin part 1

代码运行良好，但现在的问题是，当我在 localhost 中检查更新的数据时，我看到的都是空字段。下面是我设计的vb的截图。我已经根据我的数据库标记了文本框。屏幕截图中的文本框设置为在运行我的 winform 时不可见。

究竟可能是什么问题？

---

@卡卡罗特 这是我最初拥有的

MysqlConn = 新的 MySqlConnection MysqlConn.ConnectionString = "服务器=本地主机；用户ID=服务器；密码=服务器；数据库=heavisa_database" Dim rabit As MySqlDataReader

    MysqlConn.Open()

    Dim pin As String
    pin = "UPDATE heavisa_database.new_employee SET (Employee_ID = '" & txtemployeeid.Text & "', Nat_ID = '" & txtnatid.Text & "', First_Name = '" & txtfirstname.Text & "', Middle_Name = '" & txtmiddlename.Text & "', Surname = '" & txtsurname.Text & "', NSSF_No = '" & txtnssfno.Text & "', KRA_Pin = '" & txtkrapin.Text & "', NHIF_No = '" & txtnhifno.Text & "', Residence = '" & txtresidence.Text & "', Mobile_No = '" & txtmobileno.Text & "', Email = '" & txtemail.Text & "', Job_Group = '" & cbojobgroup.Text & "', Employment_Date = '" & dtpemploymentdate.Text & "') WHERE Employee_ID = '" & txtemployeeid1.Text & "'"

    Try
        con = New MySqlCommand(pin, MysqlConn)
        rabit = con.ExecuteReader

        MessageBox.Show("Update Successful.")
        MysqlConn.Close()

    Catch ex As MySqlException
        MessageBox.Show(ex.Message)
    Finally
        MysqlConn.Dispose()

    End Try

这是我目前拥有的（归功于一位 ekad 先生）

将针脚变暗为字符串 pin = "UPDATE heavisa_database.new_employee SET Employee_ID = @Employee_ID, Nat_ID = @Nat_ID, First_Name = @First_Name, Middle_Name = @Middle_Name, Surname = @Surname, NSSF_No = @NSSF_No, KRA_Pin = @KRA_Pin, NHIF_No = @NHIF_No, Residence = @Residence，Mobile_No = @Mobile_No，Email = @Email，Job_Group = @Job_Group，Employment_Date = @Employment_Date WHERE Employee_ID like '%{0}%'"

    Try
        Using MysqlConn As New MySqlConnection
            MysqlConn.ConnectionString = "server=localhost;userid=server;password=server;database=heavisa_database"

            MysqlConn.Open()

            Using con As New MySqlCommand(pin, MysqlConn)

                With con
                    con.Parameters.AddWithValue("@Employee_ID", txtemployeeid.Text)
                    con.Parameters.AddWithValue("@Nat_ID", txtnatid.Text)
                    con.Parameters.AddWithValue("@First_Name", txtfirstname.Text)
                    con.Parameters.AddWithValue("@Middle_Name", txtmiddlename.Text)
                    con.Parameters.AddWithValue("@Surname", txtsurname.Text)
                    con.Parameters.AddWithValue("@NSSF_No", txtnssfno.Text)
                    con.Parameters.AddWithValue("@KRA_Pin", txtkrapin.Text)
                    con.Parameters.AddWithValue("@NHIF_No", txtnhifno.Text)
                    con.Parameters.AddWithValue("@Residence", txtresidence.Text)
                    con.Parameters.AddWithValue("@Mobile_No", txtmobileno.Text)
                    con.Parameters.AddWithValue("@Email", txtemail.Text)
                    con.Parameters.AddWithValue("@Job_Group", cbojobgroup.Text)
                    con.Parameters.AddWithValue("@Employment_Date", dtpemploymentdate.Text)
                End With

                con.ExecuteNonQuery()
            End Using

        End Using

        MessageBox.Show("Update Successful.")
        MysqlConn.Close()

    Catch ex As MySqlException
        MessageBox.Show(ex.Message)
    End Try

第一个代码给了我一个错误（请参阅上面的链接）。第二个代码有效，但它清空了我的字段而不是更新。

Answer 1

您是如何更新数据库中的表的？它应该是这样的： （我要把我的代码用于我做的一个旧项目）

Private Sub disconnect()
    conn.Close()
End Sub

Private Sub connect()
    conn.ConnectionString = connectionString
    conn.Open()
End Sub

Private Sub btnSaveEdit_Click(sender As Object, e As EventArgs) Handles btnSaveEdit.Click

connect()
Dim query as string
Dim command As New MySqlCommand

query = "Update `tblcandidates` set firstname = '" & txtEditFname.Text & "', lastname = '" & txtEditLName.Text & "', position='" & cboEditPosition.Text & "', fullname = '" & fullname & "' where recNum = '" & txtRec.Text & "'"



command.Connection = conn
command.CommandText = query

command.ExecuteNonQuery()

disconnect()
End Sub

Answer 2

首先，只是一个简单的问题，heavisa_database.new_employee 是一张桌子吗？正确命名它们是非常明智的，如果它是一个表，你可以把tbl放在你想要的名字之前，如果它是一个数据库，你可以把db放在名字之前。只是为了防止混淆。而且我认为您在更新表中的记录时不需要reader，如果我错了，请纠正我：p

好吧，老实说，我不太了解 ekad 先生提供的代码。这是您可以尝试的代码。哦，你真的不需要SET 后面的括号。

//Global Vars
Dim connectionString As String = "server=localhost;userid=server;password=server;database=heavisa_database"
Dim conn As New MySqlConnection

首先，让我们创建一些简单的函数（您可以将其放在代码中的任何位置）：

//remember that conn is our MySqlConnection
Private Sub connect()
    conn.ConnectionString = connectionString
    conn.Open()
End Sub

Private Sub disconnect()
    conn.Close()
End Sub

所以，更新按钮的事件：

connect()

Dim pin As String
pin = "UPDATE new_employee SET Employee_ID = '" & txtemployeeid.Text & "', Nat_ID = '" & txtnatid.Text & "', First_Name = '" & txtfirstname.Text & "', Middle_Name = '" & txtmiddlename.Text & "', Surname = '" & txtsurname.Text & "', NSSF_No = '" & txtnssfno.Text & "', KRA_Pin = '" & txtkrapin.Text & "', NHIF_No = '" & txtnhifno.Text & "', Residence = '" & txtresidence.Text & "', Mobile_No = '" & txtmobileno.Text & "', Email = '" & txtemail.Text & "', Job_Group = '" & cbojobgroup.Text & "', Employment_Date = '" & dtpemploymentdate.Text & "' WHERE Employee_ID = '" & txtemployeeid1.Text & "'"

    //lets create new command
    Dim command As New MySqlCommand

    //sets the connection for our command
    command.Connection = conn
    command.CommandText = pin

    command.ExecuteNonQuery()

    disconnect()

    MessageBox.Show("Record saved!", "Success", MessageBoxButtons.OK, MessageBoxIcon.Information)

试试上面给定的代码，我很确定它会起作用。祝你好运！