MySQL 从mysql中选择放入变量VB.NET
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Select from mysql put into variable VB.NET
提问by Vinra Gunanta Pandia
I am trying to Select data from MySQL database using VB.NET
我正在尝试使用 VB.NET 从 MySQL 数据库中选择数据
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 & "'"
but i dont know how to put selected query into variable, anybody can help me ?
但我不知道如何将选定的查询放入变量中，有人可以帮助我吗？
采纳答案by Damith
you can use ExecuteScalar method as below
您可以使用 ExecuteScalar 方法，如下所示
object nama_studentObj = cmd.ExecuteScalar()
if nama_studentObj != null then
string nama_student= nama_studentObj .ToString()
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
Note :
笔记 ：
Better to use parameters when you call database, like below
调用数据库时最好使用参数，如下所示
cmd.CommandText = "SELCECT nama_student FROM student where Id_student = @Id_student"
then you have to add the parameter as
那么你必须将参数添加为
cmd.Parameters.AddWithValue("Id_student", id )
回答by Androidz
Dim StrVar as String
Dim rd As MySqlDataReader
Dim cmd as New MySqlcommand
cmd.commandtext = "Select student_name from student_table where student_id = @ID"
cmd.connection = conn
rd = cmd.ExecuteReader
if rd.read then
StrVar = rd.GetString(1)
end if
rd.close
Using the Data Reader it will let you assign the result of the query to your variable StrVar and this will come in handy. I use GetString because I assume it is a string type and GetValue for integer. The value "1" represent the column you want to pass to your variable.
使用数据读取器，它可以让您将查询结果分配给您的变量 StrVar，这将派上用场。我使用 GetString 是因为我假设它是字符串类型，而 GetValue 是整数。值“1”表示要传递给变量的列。
Let me know if this works. Cheers..Happy Coding..
让我知道这个是否奏效。干杯..快乐编码..
回答by Ruly
You can put it into DataSet
你可以把它放进 DataSet
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 id As Integer
cmd.CommandText = "SELECT nama_student FROM student where Id_student ='" & id & "'"
Dim da As New MySqlDataAdapter 'DataAdapter can be used to fill DataSet
Dim ds As New DataSet
da.SelectCommand = cmd
da.Fill(ds, "student") 'you can change student with the table name
From above command, your data will be stored in a DataSet.
从上面的命令，您的数据将存储在一个DataSet.
Sample to use:
使用示例：
ds.Tables("student").Rows.Count 'Get the number of rows in the DataTable
ds.Tables("student").Rows(0).Item("nama_student").ToString 'Get first row of the nama_student field
You can check MSDN for further information:
您可以查看 MSDN 以获取更多信息：
DataSet: http://msdn.microsoft.com/en-us/library/system.data.dataset.aspx
数据集：http: //msdn.microsoft.com/en-us/library/system.data.dataset.aspx
DataTable: http://msdn.microsoft.com/en-sg/library/system.data.datatable.aspx
数据表：http: //msdn.microsoft.com/en-sg/library/system.data.datatable.aspx
DataRow: http://msdn.microsoft.com/en-sg/library/system.data.datarow.aspx
数据行：http: //msdn.microsoft.com/en-sg/library/system.data.datarow.aspx
Note:
笔记：
As mentioned by @Joel Coehoorn, try to look at Command Parameter http://dev.mysql.com/doc/refman/5.0/es/connector-net-examples-mysqlparameter.html
正如@Joel Coehoorn 所提到的，尝试查看命令参数http://dev.mysql.com/doc/refman/5.0/es/connector-net-examples-mysqlparameter.html
