自己动手做一个SQL解释器

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。

<?php

class db_text {

var $conn;

var $classname = “db_text”;

var $databa;

function on_create() {

}

function connect($databa_name) {

$this->databa = $databa_name;

if(! file_exists($databa_name)) {

$this->conn = array();

$this->_clo();

}

$fp = fopen($this->databa,”r”);

$this->conn = unrialize(fread($fp,filesize($this->databa)));

fclo($fp);

}

function &query($query) {

if(eregi(“lect “,$query)) return $this->_lect($query);

if(eregi(“inrt “,$query)) return $this->_inrt($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 fal;

}

function num_rows($result) {

return count($result);

}

/**

* query的辅助函数

*/

function _lect($query) {

if(eregi(“(order by (.+))”,$query,$regs)) {

$order = $regs[2];

$query = eregi_replace($regs[1],””,$query);

}

if(eregi(“(group by (.+)游客的英语)”,$query,$regs)) {

$group = $regs[2];

$query = eregi_replace($regs[1],””,$query);

}

eregi(“lect .* 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];

}

}el {

$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 _inrt($query) {

eregi(peking220;inrt +into +([0-9a-z_]+) 常用韩语中文谐音*(.+) *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->_clo();

}

function _update($query) {

eregi(“update +([0-9a-z_]+) +t *(,?.*=.*)+( +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->_clo();

}

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)) {

unt($this->conn[$regs[1]][$value]);

}

ret($this->conn[$regs[1]]);

while(list($key,$value) = each($this->conn[$regs[1]])) {

$ch[] = $value;

}

$this->conn[$regs[1]] = $ch;

$this->_clo();

}

function _where($arch,$table) {

$arch = eregi_replace(“\(“,” ( “,$arch);

$arch = eregi_replace(“\)”,” ) “,$arch);

$arch = eregi_replace(“\+”,” + “,$arch);

$arch = eregi_replace(“\*”,” * “,$arch);

while(eregi(“[^ ]([*/><!=-])”,$arch,$regs)) {

$arch = eregi_replace($regs[1],” $regs[1] “,$arch);

}

while(eregi(“([><!] +=)”,$arch,$regs)) {

$arch = eregi_replace($regs[1],eregi_replace(” “,””,$regs[1]),$arch);

}

$arch = eregi_replace(”“,” “,trim($arch));

$arch = eregi_replace(” and “,” && “,$arch);

$arch = eregi_replace(” or “,” || “,$arch);

$arch = eregi_replace(” = “,” == “,$arch);

$ar = split(” “,$arch);

eval(“\$t=$table;”);

for($i=0;$i<count($ar);$i++) {

if(ist($t[0][$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);

el

usort($ar,_cmp_desc);

}

function _clo() {

$fp = fopen($this->databa,”w”);

fwrite($fp,rialize($this->conn));

fclo($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->通道磨皮connect(“text1.txt”);

$conn->query(“inrt into manage (id,title) values (10,’abcd’)”);

$conn->query(“inrt into manage (id,title) values (2,’43d’)”);

$conn->爱情不是一切query(“inrt into manage (id,title) values (20,’tuu’)”);

$conn->query(“update manage t 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(“lect * from manage where id=101 or table=’code’ group by 1 order by 1 asc”);

$rt = $conn->query(“lect * from manage group by 1 order by id desc”);

print_r($rt);

?>

</pre>