獲取表中的字段和值

Question

我有學生表包含字段：值

firstname : John 
lastname : Doe 
english-grd : 87 
math-grd : 80 
science-grd : 85 
total-grade : 0 

我的問題是我會如何獲取只能用「-GRD」的領域，總結有總。

Answer 1

查詢：

Select english-grd,math-grd,science-grd,(english-grd+math-grd+science-grd) as tot from table 

Answer 2

update tableName set `total-grade` = (
`english-grd` + `math-grd` + `science-grd` 
) 

Answer 3

// this example just update one row 
$student_id = 1; // example only 
$res=mysql_query("SELECT * FROM Student where student_id='" . $student_id . "'"); 
$field_count = mysql_num_fields($res); //count field numbers 
$total_grades = 0; 
for ($i = 0; $i < $field_count; $i++) 
{ 
    $field_name=mysql_field_name($res, $i); 
    if (substr($field_name,-4) == '-grd') 
    { 
     $total_grades = $total_grades + mysql_result($res,0,$i); // 0 refer to first row ...there is only one row from $res...$i is offset of the column 
    } 
} 
mysql_query("update Student SET total-grade='" . $total_grades . "' where student_id='" . $student_id . "'");