how to update column in database MySQL

I am trying to update my database column, using data from datagridview column. I am using MySQL for database and vb.net for program.

This is my code:

cmd = New MySqlCommand("UPDATE tb_poinjalan 
      SET Bobot ='" & DataGridView2.Item(4, i).Value 
      & "' WHERE Kriteria='" & DataGridView2.Item(1, i).Value 
      & "';", Connector)

The problem is, this code only change first row in database column.

#vb.net #mysql