vb.net 需要从 sql 查询中获取值
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need to get value from sql query
提问by Nate Pet
Through ADO,I like to do the following query:
通过ADO，我喜欢做以下查询：
select name, address, zip from terr where id = '33334'
I like then to assign name, addess, zip to variables so that I can assign it later in my program. How do I do this with VB.NET ADO?
我喜欢然后将名称，地址，zip 分配给变量，以便我稍后可以在我的程序中分配它。如何使用 VB.NET ADO 执行此操作？
回答by Robert Beaubien
Try somethign like this:
尝试这样的事情：
Dim dbName As String
Dim dbAddress As String
Dim dbZip As String
Using connObj As New SqlClient.SqlConnection("<connectionString>")
Using cmdObj As New SqlClient.SqlCommand("select name, address, zip from terr where id = '33334'", connObj)
connObj.Open()
Using readerObj As SqlClient.SqlDataReader = cmdObj.ExecuteReader
'This will loop through all returned records
While readerObj.Read
dbName = readerObj("name").ToString
dbAddress = readerObj("address").ToString
dbZip = readerObj("zip").ToString
'handle returned value before next loop here
End While
End Using
connObj.Close()
End Using
End Using
Also, you should look into parameterizing the value for the where clause.
此外，您应该研究参数化 where 子句的值。
回答by Tim Schmelter
You need a DataBase (i assume MS Sql-Server), a Connection and a DataAdapter to fill a DataTable. Then you have all you need. Here's an example:
您需要一个数据库（我假设是 MS Sql-Server）、一个连接和一个 DataAdapter 来填充 DataTable。然后你就拥有了你需要的一切。下面是一个例子：
Public Function GetUser(UserId As Int32) As DataRow
Using con = New SqlConnection(My.Settings.RM2ConnectionString)
Using cmd = New SqlCommand("select name, address, zip from terr where id = @id", con)
cmd.Parameters.AddWithValue("@id", UserId)
Dim da = New SqlDataAdapter(cmd)
Dim tblUser = New DataTable
da.Fill(tblUser)
If tblUser.Rows.Count <> 0 Then
Return tblUser(0)
Else
Return Nothing
End If
End Using
End Using
End Function
回答by seba123neo
execute a SqlCommand from SQLDatareader, like:
从 SQLDatareader 执行 SqlCommand，例如：
Dim vVendedor As New SqlCommand("SELECT user FROM users", mConeccion)
vDatosVen = vVendedor.ExecuteReader
vVendedor = Nothing
and to get te value:
并获得 te 值：
While vDatosVen.Read()
vUser = vDatosVen("user")
End While
回答by Samuel
Here's what i did...
这就是我所做的...
Private Sub btn_Connect_Click(sender As Object, e As EventArgs) Handles btn_Connect.Click
Dim sql_connection As New MySqlConnection
Dim sql_query As New MySqlCommand
Dim sql_result As MySqlDataReader
sql_connection.ConnectionString = "Server=localhost;Database=hidden;Uid=root;Pwd=;"
sql_query.Connection = sql_connection
sql_connection.Open()
sql_query.CommandText = "SELECT Entry,name FROM table WHERE entry=1;"
sql_result = sql_query.ExecuteReader
If sql_result.HasRows Then
Do While sql_result.Read()
Dim query_result As String
query_result = sql_result("name")
MsgBox(query_result)
Loop
Else
MsgBox("No results found.")
End If
