mysql - 如何在 vb.net 中检索 mysql 数据？

Question

我正在尝试检索具有特定列的 mysql 数据并显示到 vb.net 中的文本框。我应该如何取回它？

Dim connect As New MySqlConnection("server=localhost; user id=root; password= ; database=ticketing_system;")
    connect.Open()

    Dim sqladapter As New MySqlDataAdapter
    Dim sqlcmd As New MySqlCommand
    Dim dr As MySqlDataReader
    Dim dt As New DataTable

    sqlcmd = New MySqlCommand("SELECT * complaint WHERE tran_no='" & lbltranno.Text & "'")
    **THEN? WHAT SHOULD I DO TO DISPLAY DATA? PLEASE HELP**

    connect.Close()

Answer 1

您只是缺少 Execution 方法。这取决于你想要什么样的结果。如果您只想要查询的第一个结果(第一行和第一列)，则使用 sqlcmd.ExecuteScalar()。

如果你想要所有的结果，你必须使用 sqlcmd.ExecuteReader() 方法将其加载到 MySqlDataReader

使用 ExecuteReader() :

Dim connect As New MySqlConnection("server=localhost; user id=root; password= ; database=ticketing_system;")
connect.Open()

Dim sqladapter As New MySqlDataAdapter
Dim sqlcmd As New MySqlCommand
Dim dr As MySqlDataReader
Dim dt As New DataTable

sqlcmd = New MySqlCommand("SELECT * complaint WHERE tran_no='" & lbltranno.Text & "'")
dr = sqlcmd.ExecuteReader()
dt.Load(dr)
'Useable datatable in dt variable...

connect.Close()

使用 ExecuteScalar() :

Dim connect As New MySqlConnection("server=localhost; user id=root; password= ; database=ticketing_system;")
connect.Open()

Dim sqladapter As New MySqlDataAdapter
Dim sqlcmd As New MySqlCommand
Dim dr As String
Dim dt As New DataTable

sqlcmd = New MySqlCommand("SELECT [COLUMN NAME] complaint WHERE tran_no='" & lbltranno.Text & "'")
dr = sqlcmd.ExecuteScalar()
'dr now contains the value of [COLUMN NAME] for the first returned row.

connect.Close()