vb.net 从 sql-query 获取单个值到文本框中
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get single value from sql-query into a textbox
提问by ruedi
The result of my sql-query is a single value i want display that in a lable but dont know how. I have a solution creating a dataset put the result of the query into that dataset and get it by row(0),column(0) but i guess there is a smarter way doing it.
我的 sql-query 的结果是我想在标签中显示但不知道如何显示的单个值。我有一个创建数据集的解决方案，将查询结果放入该数据集并按行（0），列（0）获取它，但我想有一种更聪明的方法。
Private myquery As String
Sub New(ByVal query As String)
myquery = query
End Sub
Public Sub query_Send()
Dim myconn As New SqlConnection("Data Source=DB;Integrated Security=TRUE")
Dim mycmd As SqlCommand = New SqlCommand(Me.myQuery, myconn)
Dim myTable As New DataTable
Dim previousConnectionState As ConnectionState = myconn.State
Try
If myconn.State = ConnectionState.Closed Then
myconn.Open()
Dim myDA As New SqlDataAdapter(mycmd)
myDA.Fill(myTable)
tb.text = **...**
End If
If previousConnectionState = ConnectionState.Closed Then
myconn.Close()
End If
End Try
End Sub
回答by IvanH
You can use SqlCommand.ExecuteScalar Method
您可以使用SqlCommand.ExecuteScalar 方法
Dim querystr as String = "select value from MyTable where ID=5"
Dim mycmd As New SqlCommand(querystr, connection)
dim value as Object = mycmd.ExecuteScalar()
The valueyou can put to your textbox. ExecuteScalar returns first value of first row of the resultset (equivalent of row(0).column(0)) When no record is returned the valueis nothing.
在value你可以把你的文本。ExecuteScalar 返回结果集第一行的第一个值（相当于row(0).column(0)） 当没有记录返回时value是nothing。
回答by Derek Meyer
Try something more along the lines of:
尝试更多的东西：
Using myconn As New SqlConnection("Data Source=DB;Integrated Security=TRUE")
Dim myDA As New SqlDataAdapter()
myDA.SelectCommand = New SqlCommand(myQuery, myconn)
myDA.Fill(myTable)
Return myTable
End Using
Or you can just get ahold of the first item in the first row with
或者您可以使用以下命令获取第一行中的第一项
myTable.Rows(0).ItemArray(0).ToString()
myTable.Rows(0).ItemArray(0).ToString()
