自己动手做一个sql解释器
在一些小型的应用中，完全没有必要使用大型数据库软件。自己做一个sql解释器就能用数据库的方式来管理了。
这个解释器，能解释常用的sql命令。你可以自行添加其他功能。
database = $database_name;
    if(! file_exists($database_name)) {
      $this->conn = array();
      $this->_close();
    }
    $fp = fopen($this->database,r);
    $this->conn = unserialize(fread($fp,filesize($this->database)));
    fclose($fp);
  }
  function &query($query) {
    if(eregi(select ,$query)) return $this->_select($query);
    if(eregi(insert ,$query)) return $this->_insert($query);
    if(eregi(delete ,$query)) return $this->_delete($query);
    if(eregi(update ,$query)) return $this->_update($query);
    return array();
  }
  function fetch_row(&$result) {
    if(list($key,$value) = each($result))
      return $value;
    return false;
  }
  function num_rows($result) {
    return count($result);
  }
/**
   * query的辅助函数
   */
  function _select($query) {
    if(eregi((order by (.+)),$query,$regs)) {
      $order = $regs[2];
      $query = eregi_replace($regs[1],,$query);
    }
    if(eregi((group by (.+)),$query,$regs)) {
      $group = $regs[2];
      $query = eregi_replace($regs[1],,$query);
    }
    eregi(select .* from ([0-9a-z_]+) *(where +(.+))?,$query,$regs);
    if($regs[3] != ) {
      $keys = $this->_where($regs[3],\$this->conn[$regs[1]]);
      while(list($key,$value) = each($keys)) {
        $rs[] = $this->conn[$regs[1]][$value];
      }
    }else {
      $rs = $this->conn[$regs[1]];
    }
    if($order) {
      sscanf($order,%s %s,$key,$type);
      if(empty($type)) $type = asc;
        $this->_sort($rs,$key,$type);
    }
    return $rs;
  }
  function _insert($query) {
    eregi(insert +into +([0-9a-z_]+) *(.+) *values? *(.+),$query,$regs);
    eval(\$key=array$regs[2];);
    eval(\$value=array$regs[3];);
    for($i=0;$i      $rs[$key[$i]] = $value[$i];
    $this->conn[$regs[1]][] = $rs;
    $this->_close();
  }
  function _update($query) {
    eregi(update +([0-9a-z_]+) +set *(,?.*=.*)+( +where +(.+)),$query,$regs);
    $regs[2] = eregi_replace(,,=,$regs[2]);
    $v = split(=,$regs[2]);
    $keys = $this->_where($regs[4],\$this->conn[$regs[1]]);
    while(list($key,$value) = each($keys)) {
      for($i=0;$i        $this->conn[$regs[1]][$value][$v[$i]] = eregi_replace(',,$v[$i+1]);
    }
    $this->_close();
  }
  function _delete($query) {
    eregi(delete +from +([0-9a-z_]+) *(where +(.+))?,$query,$regs);
    $keys = $this->_where($regs[3],\$this->conn[$regs[1]]);
    while(list($key,$value) = each($keys)) {
      unset($this->conn[$regs[1]][$value]);
    }
    reset($this->conn[$regs[1]]);
    while(list($key,$value) = each($this->conn[$regs[1]])) {
      $ch[] = $value;
    }
    $this->conn[$regs[1]] = $ch;
    $this->_close();
  }
  function _where($search,$table) {
    $search = eregi_replace(\(, ( ,$search);
    $search = eregi_replace(\), ) ,$search);
    $search = eregi_replace(\+, + ,$search);
    $search = eregi_replace(\*, * ,$search);
    while(eregi([^ ]([*/>      $search = eregi_replace($regs[1], $regs[1] ,$search);
    }
    while(eregi(([>      $search = eregi_replace($regs[1],eregi_replace( ,,$regs[1]),$search);
    }
    $search = eregi_replace(  , ,trim($search));
    $search = eregi_replace( and , && ,$search);
    $search = eregi_replace( or , || ,$search);
    $search = eregi_replace( = , == ,$search);
    $ar = split( ,$search);
    eval(\$t=$table;);
for($i=0;$i      if(isset($t[0][$ar[$i]]))
        $ar[$i] = \$value[.$ar][$i].];
    }
    $expr = \$expl=(.join( ,$ar).);;
while(list($key,$value) = each($t)) {
      eval($expr);
      if($expl)
        $keys[] = $key;
    }
    return $keys;
  }
  function _sort(&$ar,$key=0,$mode=desc) {
    global $cmp_key;
    $cmp_key = $key;
    if($mode == asc)
      usort($ar,_cmp_asc);
    else
      usort($ar,_cmp_desc);
  }
  function _close() {
    $fp = fopen($this->database,w);
    fwrite($fp,serialize($this->conn));
    fclose($fp);
  }
}
/** 排序键
*/
$cmp_key = ;
/** 排序用工作函数(降序 由usort()调用)
*/
function _cmp_desc($a,$b) {
  global $cmp_key;
  if ($a[$cmp_key] == $b[$cmp_key]) return 0;
  return ($a[$cmp_key] > $b[$cmp_key]) ? -1 : 1;
}
/** 排序用工作函数(升序 由usort()调用)
*/
function _cmp_asc($a,$b) {
  global $cmp_key;
  if ($a[$cmp_key] == $b[$cmp_key]) return 0;
  return ($a[$cmp_key] > $b[$cmp_key]) ? 1 : -1;
}
?>
测试例：
connect(text1.txt);
$conn->query(insert into manage (id,title) values (10,'abcd'));
$conn->query(insert into manage (id,title) values (2,'43d'));
$conn->query(insert into manage (id,title) values (20,'tuu'));
$conn->query(update manage set id=101,test='a' where id=10);
//$conn->query(delete from manage where id='10');
//$conn->query(delete from manage where id=10 or table='code');
//$rt = $conn->query(select * from manage where id=101 or table='code' group by 1 order by 1 asc);
$rt = $conn->query(select * from manage group by 1 order by id desc);
print_r($rt);
?>

http://www.bkjia.com/phpjc/315042.htmlwww.bkjia.comtruehttp://www.bkjia.com/phpjc/315042.htmltecharticle自己动手做一个sql解释器 在一些小型的应用中，完全没有必要使用大型数据库软件。自己做一个sql解释器就能用数据库的方式来管理了。...