sql语句 case

case：

SELECT stdname,
max( CASE WHEN stdsubject = '语文' THEN  result ELSE 0 END) "语文",
max( CASE WHEN stdsubject = '数学' THEN  result ELSE 0 END) "数学",
max( CASE WHEN stdsubject = '物理' THEN  result ELSE 0 END) "物理" ,
max( CASE WHEN stdsubject = '化学' THEN result ELSE 0 END)  "化学"
FROM  std
GROUP BY stdname;