MySQL方式操作文本数据库

tznktg

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。

1. <?php
   
2. class DB_text {
   
3. var $conn;
   
4. var $classname = "db_text";
   
5. var $database;
   
6. function on_create() {
   
7. }
   
8. function connect($database_name) {
   
9. $this->database = $database_name;
   
10. if(! file_exists($database_name)) {
    
11. $this->conn = array();
    
12. $this->_close();
    
13. }
    
14. $fp = fopen($this->database,"r");
    
15. $this->conn = unserialize(fread($fp,filesize($this->database)));
    
16. fclose($fp);
    
17. }
    
18. function &query($query) {
    
19. if(eregi("select ",$query)) return $this->_select($query);
    
20. if(eregi("insert ",$query)) return $this->_insert($query);
    
21. if(eregi("delete ",$query)) return $this->_delete($query);
    
22. if(eregi("update ",$query)) return $this->_update($query);
    
23. return array();
    
24. }
    
25. function fetch_row(&$result) {
    
26. if(list($key,$value) = each($result))
    
27. return $value;
    
28. return false;
    
29. }
    
30. function num_rows($result) {
    
31. return count($result);
    
32. }
    
33. 
    
34. /**
    
35. * query的辅助函数
    
36. */
    
37. function _select($query) {
    
38. if(eregi("(order by (.+))",$query,$regs)) {
    
39. $order = $regs[2];
    
40. $query = eregi_replace($regs[1],"",$query);
    
41. }
    
42. if(eregi("(group by (.+))",$query,$regs)) {
    
43. $group = $regs[2];
    
44. $query = eregi_replace($regs[1],"",$query);
    
45. }
    
46. eregi("select .* from ([0-9a-z_]+) *(where +(.+))?",$query,$regs);
    
47. if($regs[3] != "") {
    
48. $keys = $this->_where($regs[3],"\$this->conn[$regs[1]]");
    
49. while(list($key,$value) = each($keys)) {
    
50. $rs[] = $this->conn[$regs[1]][$value];
    
51. }
    
52. }else {
    
53. $rs = $this->conn[$regs[1]];
    
54. }
    
55. if($order) {
    
56. sscanf($order,"%s %s",$key,$type);
    
57. if(empty($type)) $type = "asc";
    
58. $this->_sort($rs,$key,$type);
    
59. }
    
60. return $rs;
    
61. }
    
62. function _insert($query) {
    
63. eregi("insert +into +([0-9a-z_]+) *(.+) *values? *(.+)",$query,$regs);
    
64. eval("\$key=array$regs[2];");
    
65. eval("\$value=array$regs[3];");
    
66. for($i=0;$i<count($key);$i++)
    
67. $rs[$key[$i]] = $value[$i];
    
68. $this->conn[$regs[1]][] = $rs;
    
69. $this->_close();
    
70. }
    
71. function _update($query) {
    
72. eregi("update +([0-9a-z_]+) +set *(,?.*=.*)+( +where +(.+))",$query,$regs);
    
73. $regs[2] = eregi_replace(",","=",$regs[2]);
    
74. $v = split("=",$regs[2]);
    
75. $keys = $this->_where($regs[4],"\$this->conn[$regs[1]]");
    
76. while(list($key,$value) = each($keys)) {
    
77. for($i=0;$i<count($v);$i+=2)
    
78. $this->conn[$regs[1]][$value][$v[$i]] = eregi_replace("'","",$v[$i+1]);
    
79. }
    
80. $this->_close();
    
81. }
    
82. function _delete($query) {
    
83. eregi("delete +from +([0-9a-z_]+) *(where +(.+))?",$query,$regs);
    
84. $keys = $this->_where($regs[3],"\$this->conn[$regs[1]]");
    
85. while(list($key,$value) = each($keys)) {
    
86. unset($this->conn[$regs[1]][$value]);
    
87. }
    
88. reset($this->conn[$regs[1]]);
    
89. while(list($key,$value) = each($this->conn[$regs[1]])) {
    
90. $ch[] = $value;
    
91. }
    
92. $this->conn[$regs[1]] = $ch;
    
93. $this->_close();
    
94. }
    
95. function _where($search,$table) {
    
96. $search = eregi_replace("\("," ( ",$search);
    
97. $search = eregi_replace("\)"," ) ",$search);
    
98. $search = eregi_replace("\+"," + ",$search);
    
99. $search = eregi_replace("\*"," * ",$search);
    
100. while(eregi("[^ ]([*/><!=-])",$search,$regs)) {
     
101. $search = eregi_replace($regs[1]," $regs[1] ",$search);
     
102. }
     
103. while(eregi("([><!] +=)",$search,$regs)) {
     
104. $search = eregi_replace($regs[1],eregi_replace(" ","",$regs[1]),$search);
     
105. }
     
106. $search = eregi_replace(" "," ",trim($search));
     
107. $search = eregi_replace(" and "," && ",$search);
     
108. $search = eregi_replace(" or "," || ",$search);
     
109. $search = eregi_replace(" = "," == ",$search);
     
110. $ar = split(" ",$search);
     
111. eval("\$t=$table;");
     
112. 
     
113. for($i=0;$i<count($ar);$i++) {
     
114. if(isset($t[0][$ar[$i]]))
     
115. $ar[$i] = "\$value[".$ar][$i]."]";
     
116. }
     
117. $expr = "\$expl=(".join(" ",$ar).");";
     
118. 
     
119. while(list($key,$value) = each($t)) {
     
120. eval($expr);
     
121. if($expl)
     
122. $keys[] = $key;
     
123. }
     
124. return $keys;
     
125. }
     
126. function _sort(&$ar,$key=0,$mode="desc") {
     
127. global $cmp_key;
     
128. $cmp_key = $key;
     
129. if($mode == "asc")
     
130. usort($ar,_cmp_asc);
     
131. else
     
132. usort($ar,_cmp_desc);
     
133. }
     
134. function _close() {
     
135. $fp = fopen($this->database,"w");
     
136. fwrite($fp,serialize($this->conn));
     
137. fclose($fp);
     
138. }
     
139. }
     
140. 
     
141. /** 排序键
     
142. */
     
143. $cmp_key = "";
     
144. 
     
145. /** 排序用工作函数(降序 由usort()调用)
     
146. */
     
147. function _cmp_desc($a,$b) {
     
148. global $cmp_key;
     
149. if ($a[$cmp_key] == $b[$cmp_key]) return 0;
     
150. return ($a[$cmp_key] > $b[$cmp_key]) ? -1 : 1;
     
151. }
     
152. 
     
153. /** 排序用工作函数(升序 由usort()调用)
     
154. */
     
155. function _cmp_asc($a,$b) {
     
156. global $cmp_key;
     
157. if ($a[$cmp_key] == $b[$cmp_key]) return 0;
     
158. return ($a[$cmp_key] > $b[$cmp_key]) ? 1 : -1;
     
159. }
     
160. ?>
     
161. 
     
162. 测试例：
     
163. <?php
     
164. //require_once "db_text.php";
     
165. 
     
166. $conn = new DB_text;
     
167. $conn->connect("text1.txt");
     
168. 
     
169. $conn->query("insert into manage (id,title) values (10,'abcd')");
     
170. $conn->query("insert into manage (id,title) values (2,'43d')");
     
171. $conn->query("insert into manage (id,title) values (20,'tuu')");
     
172. $conn->query("update manage set id=101,test='a' where id=10");
     
173. //$conn->query("delete from manage where id='10'");
     
174. //$conn->query("delete from manage where id=10 or table='code'");
     
175. 
     
176. 
     
177. //$rt = $conn->query("select * from manage where id=101 or table='code' group by 1 order by 1 asc");
     
178. $rt = $conn->query("select * from manage group by 1 order by id desc");
     
179. 
     
180. print_r($rt);
     
181. 
     
182. ?>

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