what is wrong with the second code?

Question

I have a code used to update mysql table. the first one is able to but the second one does not. What is the difference between the two codes apart from tables and the other components

[code]
                accessDB1.connection();
                string up = "update payment set dues = '" + txtDues.Text + "'";
                accessDB1.myCmd(up).ExecuteNonQuery();
[/code]

[code]
                //this does not update
                soo.connection();
                string soob = "Update terminals  set computername = '" + txtcompname.Text + "',location='" + txtcomploc.Text + "' where termid = '" + terminalid.Text + "'";
                soo.myCmd(soob).ExecuteNonQuery();
[/code]