Select from mysql put into variable VB.NET - mysql

Question

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

Answer 1

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.
Let me know if this works. Cheers..Happy Coding..

Answer 2

you can use ExecuteScalar method as below
object nama_studentObj = cmd.ExecuteScalar()
if nama_studentObj != null then
string nama_student= nama_studentObj .ToString()
Full example code
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 :
Better to use parameters when you call database, like below
cmd.CommandText = "SELCECT nama_student FROM student where Id_student = #Id_student"
then you have to add the parameter as
cmd.Parameters.AddWithValue("Id_student", id )
How do I create a parameterized SQL query? Why Should I?

Answer 3

You can put it into 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.
Sample to use:
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:
DataSet: http://msdn.microsoft.com/en-us/library/system.data.dataset.aspx
DataTable: http://msdn.microsoft.com/en-sg/library/system.data.datatable.aspx
DataRow: http://msdn.microsoft.com/en-sg/library/system.data.datarow.aspx
Note:
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