从mysql中选择放入变量VB.NET [英] Select from mysql put into variable VB.NET

问题描述

我正在尝试使用VB.NET从MySQL数据库中选择数据

I am trying to Select data from MySQL database using VB.NET

Dim conn As New MySqlConnection
    Dim cmd As New MySqlCommand
    conn.ConnectionString = "Server=localhost; user id=root; password=; database=aplikasi_store_testing;"
    cmd.Connection = conn
    conn.Open()

    Dim Number As Integer
    cmd.CommandText = "SELCECT nama_student  FROM student where Id_student ='" & id & "'" 

但我不知道如何将所选查询放入变量中， 有人可以帮助我吗?

but i dont know how to put selected query into variable, anybody can help me ?

推荐答案

您可以使用ExecuteScalar方法，如下所示

you can use ExecuteScalar method as below

object nama_studentObj = cmd.ExecuteScalar()
if nama_studentObj != null then
  string nama_student= nama_studentObj .ToString()

完整的示例代码

    Dim cs As String = "Database=testdb;Data Source=localhost;" _
        & "User Id=testuser;Password=test623"

    Dim stm As String = "SELECT VERSION()"
    Dim version As String
    Dim conn As MySqlConnection

    Try
        conn = New MySqlConnection(cs)
        conn.Open()

        Dim cmd As MySqlCommand = New MySqlCommand(stm, conn)

        version = Convert.ToString(cmd.ExecuteScalar())

        Console.WriteLine("MySQL version: {0}", version)

    Catch ex As MySqlException
        Console.WriteLine("Error: " & ex.ToString())
    Finally
        conn.Close()
    End Try

注意:

调用数据库时最好使用参数，如下所示

Note :

Better to use parameters when you call database, like below

cmd.CommandText = "SELCECT nama_student  FROM student where Id_student = @Id_student"

然后您必须将参数添加为

then you have to add the parameter as

cmd.Parameters.AddWithValue("Id_student", id )

如何创建参数化的SQL询问?为什么要我?

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