スマートな SQL

public functions getName(){   $sql=sprintf("select pin,point from table");   $results = array();   if(!$error=$this->db->query($sql)) {      $name = $this->getSn($results['pin']);      $this->hlist[] = $results;   }   $this->db->free();   $this->db2->free();   return $this->hlist;}public function getSn($pin){   $sql = sprintf("SELECT sn FROM `%s_pin` WHERE pin=%s",__MYSQL_PREFIX,$pin);   return $this->db2->get_one($sql);}

$sql=sprintf("select id,seriesid,name from category"); if(!$error=$this->db->query($sql)) {      $name = $this->getName($results['seriesid']);      $results['seriesid']=$name['name'];      $this->hlist[] = $results;   } return $this->hlist;//我想把从category表里读取出来的seriesid替换成对应的名字//但是用这种方法,在页面打开的时候要等很久,请问可以怎么优化??function getName($seriesid){   $sql=sprintf("select name from series where id=$seriesid");   return $this->db2->get_one($sql);}