从c＃winforms中的另一个sql表中查找值

Question

我正在使用c＃winform，当用户在State字段中输入内容时，我想在另一个表中查找该值并找到该代码。我已经评论了下面关于我尝试过的内容，但是没有用到

 MySqlCommand cmdDatabase = new MySqlCommand(" update `STUDENT REGISTER` INNER JOIN `States` ON `STUDENT REGISTER`.`State` = `States`.`State Code` set " +
                "`first Name`='" + cboStudentFirstName.Text.Trim() + "'," +
                 "`Surname`='" + cboStudentSurname.Text.Trim() + "'," +

//如果此人在此表上选择输入VIC，我希望它在名为states的表中查找该值，并将该状态的代码返回给我                      “STUDENT REGISTER。State = States。State Code，”+