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。<?phpclass DB_text { var $conn; var $classname = "db_text"; var $database; function on_create() { } function connect($database_name) { $this->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<count($key);$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;$i<count($v);$i+=2) $this->conn[$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("[^ ]([*/><!=-])",$search,$regs)) { $search = eregi_replace($regs[1]," $regs[1] ",$search); } while(eregi("([><!] +=)",$search,$regs)) { $search = eregi_replace($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<count($ar);$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：<pre><?php//require_once "db_text.php";$conn = new DB_text;$conn->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);?></pre>
