项目开始阶段使用mysql数据库开发，后期改成oracle。数据抽象Db类对sql语句进行了封装，所以我主要工作就是参照mysql驱动的接口写一个oracle驱动。
基本的siud操作两者差别不是特别大，只有个别地方需要做一些工作：
- 在oracle中建立相应的序列和触发器，实现mysql中的auto_increment字段
- 使用子查询，实现mysql的limit以及sql_calc_found_rows功能
- 对sql语句进行替换，避免mysql不出问题的字符或关键字在oracle中出问题
最后有两个问题比较致命：
- 联表查询的时候会出现“列定义不明确”的错误
- 分组查询的时候会出现“不是一个group查询”的错误
对于前者，原因就是a表中有字段xx，b表中也有字段xx，然后select a.*, b.*就会出现错误了。
对于后者，就是oracle中对group查询有这样的限制，select的字段、order中使用的字段，要么是出现在group by中，要么是被统计函数作用。而在mysql中却没有这样的限制。
这两个致命问题，我开始时是想要在oracle驱动上对sql语句进行hack，但是测试了一些例子发现没有什么规律而言，而且数据库驱动不维持表的元信息，所以写起来比较困难，就算最后写出来，执行效率也不高。最后只能返回去改程序，同时也给自己长记性，要改改在mysql中养成的那些臭毛病。
此外还有一些需要注意的地方，比如：
- 字段类型的转换
- NULL的问题
- 单双引号
最后上代码：
1 <?php 2 define(\'_TS\', microtime(true)); 3 error_reporting(E_ALL); 4 header(\'Content-type: text/plain; charset=utf-8\'); 5 6 $_db = \'dbname\'; 7 $_prefix = \'pre_\'; 8 $_new_prefix = \'pre2_\'; 9 10 $_sql_table = "select table_name, auto_increment, table_comment from information_schema.tables where table_schema = \'".$_db."\' and table_name like \'".$_prefix."%\';"; 11 $_sql_column = "select column_name, column_default, is_nullable, column_type, column_key, extra, column_comment from information_schema.columns where table_schema = \'".$_db."\' and table_name = \'".$_prefix."%s\' order by ordinal_position;"; 12 $_sql_checknull = "select count(*) from %s where %s = \'\' or %s is null"; 13 14 $db = mysql_connect(\'localhost\', \'root\', \'\'); 15 mysql_select_db($_db); 16 mysql_query(\'set names utf8;\'); 17 18 function query($sql, $mode = MYSQL_ASSOC) 19 { 20 $q = mysql_query($sql); 21 if (!$q) 22 exit(\'query error: \'. mysql_error()); 23 24 $ret = array(); 25 while ($tmp = mysql_fetch_array($q, $mode)) 26 $ret[] = $tmp; 27 28 return $ret; 29 } 30 31 echo \'SET DEFINE OFF;\'. PHP_EOL; 32 33 foreach (query($_sql_table) as $table) 34 { 35 $t = substr($table[\'table_name\'], strlen($_prefix)); 36 if (!$t) 37 exit("unknown table: {$t}"); 38 39 $new_table_name = $_new_prefix. $t; 40 41 echo \'-- \'. $t. PHP_EOL; 42 echo \'DROP TABLE \'. $new_table_name. \';\'. PHP_EOL; 43 echo \'CREATE TABLE \'. $new_table_name. PHP_EOL; 44 echo \'(\'. PHP_EOL; 45 46 $pks = array(); 47 $idx = array(); 48 $aic = \'\'; 49 $comments = \'\'; 50 51 $cArr = query(sprintf($_sql_column, $t)); 52 $i = count($cArr); 53 foreach ($cArr as $c) 54 { 55 if ($c[\'extra\'] == \'auto_increment\') 56 $aic = $c[\'column_name\']; 57 58 echo $c[\'column_name\']. \' \'; 59 if (!preg_match(\'/^(\w+)\b[^\d]*(\d+)?[^\d]*(\d+)?/\', $c[\'column_type\'], $match)) 60 exit("cannot match: {$t}.{$c[\'column_name\']}"); 61 62 array_shift($match); 63 $type = strtolower(array_shift($match)); 64 switch ($type) 65 { 66 case \'mediumint\': 67 case \'int\': 68 case \'tinyint\': 69 echo \'NUMBER(\'. ($match[0] < 5 ? 5 : $match[0]). \')\'; 70 break; 71 case \'decimal\': 72 echo \'NUMBER(\'. $match[0]. \',\'. $match[1]. \')\'; 73 break; 74 case \'char\': 75 case \'varchar\': 76 $match[0] *= 2; 77 echo \'VARCHAR2(\'. ($match[0] > 4000 ? 4000 : $match[0]). \')\'; 78 break; 79 case \'date\': 80 case \'enum\': 81 echo \'VARCHAR2(10)\'; 82 break; 83 case \'text\': 84 echo \'NCLOB\'; 85 break; 86 default: 87 exit("unknown type: {$c[\'column_name\']} {$type}"); 88 } 89 90 if ($c[\'column_default\'] !== null) 91 echo " DEFAULT \'". $c[\'column_default\']. "\'"; 92 93 switch (strtoupper($c[\'column_key\'])) 94 { 95 case \'PRI\': 96 $pks[] = $c[\'column_name\']; 97 break; 98 case \'MUL\': 99 $idx[$c[\'column_name\']] = \'INDEX\'; 100 break; 101 case \'UNI\': 102 $idx[$c[\'column_name\']] = \'UNIQUE INDEX\'; 103 break; 104 } 105 106 if (strtoupper($c[\'is_nullable\']) == \'NO\') 107 { 108 $checknull = query(sprintf($_sql_checknull, $table[\'table_name\'], $c[\'column_name\'], $c[\'column_name\']), MYSQL_NUM); 109 if (!(int) $checknull[0][0]) 110 echo \' NOT NULL\'; 111 } 112 113 if (--$i) 114 echo \',\'; 115 116 echo PHP_EOL; 117 118 $comments .= \'COMMENT ON COLUMN \'. $new_table_name. \'.\'. $c[\'column_name\']; 119 $comments .= " IS \'". $c[\'column_comment\']. "\';". PHP_EOL; 120 } 121 122 if (count($pks)) 123 echo \', PRIMARY KEY (\'.implode(\', \', $pks).\')\'. PHP_EOL; 124 125 echo \');\'. PHP_EOL; 126 127 foreach ($idx as $k => $v) 128 echo \'CREATE \'. $v. \' \'. $new_table_name. \'_\'. $k. \' ON \'. $new_table_name. \' (\'. $k. \');\'. PHP_EOL; 129 130 echo \'COMMENT ON TABLE \'. $new_table_name. " IS \'". addslashes($table[\'table_comment\']). "\';". PHP_EOL; 131 echo $comments; 132 133 foreach (query("select * from {$table[\'table_name\']}") as $row) 134 { 135 echo \'INSERT INTO \'. $new_table_name. \' VALUES (\'; 136 foreach ($row as & $ri) 137 $ri = "\'".addslashes($ri)."\'"; 138 139 echo implode(\',\', $row); 140 echo \');\'. PHP_EOL; 141 } 142 143 if ($aic) 144 { 145 echo \'DROP SEQUENCE SEQU_\'. $t. \';\'. PHP_EOL; 146 echo \'CREATE SEQUENCE SEQU_\'. $t. \' MINVALUE 1 MAXVALUE 999999999999 INCREMENT BY 1\'. PHP_EOL; 147 echo \'START WITH \'. $table[\'auto_increment\']. \' NOCACHE ORDER NOCYCLE ;\'. PHP_EOL; 148 echo \'CREATE OR REPLACE TRIGGER TRIG_\'. $t. \'\'. PHP_EOL; 149 echo \'BEFORE INSERT ON \'. $new_table_name. \'\'. PHP_EOL; 150 echo \'FOR EACH ROW\'. PHP_EOL; 151 echo \'BEGIN\'. PHP_EOL; 152 echo \' SELECT SEQU_\'. $t. \'.NEXTVAL INTO :NEW.\'.$aic.\' FROM DUAL;\'. PHP_EOL; 153 echo \'END;\'. PHP_EOL; 154 echo \'/\'. PHP_EOL; 155 } 156 157 echo PHP_EOL; 158 } 159 160 mysql_close($db); 161 echo \'-- \'; 162 printf(\'%.3f\', microtime(true) - _TS);
<?php // 比较关键的一些操作 // connect $linkId = oci_new_connect(\'user\', \'pass\', \'host/sid\', \'utf8\'); // query $stmt = oci_parse($linkId, $sql); $mode = false ? OCI_DEFAULT : OCI_COMMIT_ON_SUCCESS; if (!oci_execute($stmt, $mode)) throw new Exception(\'query error: \'. $sql); // fetch $ret = array(); while ($tmp = oci_fetch_array($stmt, OCI_BOTH + OCI_RETURN_NULLS + OCI_RETURN_LOBS)) $ret[] = array_change_key_case($tmp); // select $sql = \'select %s \'; $sql .= \'from %s \'; $sql .= \'left join %s on %s \'; $sql .= \'where %s \'; $sql .= \'group by %s \'; $sql .= \'having %s \'; $sql .= \'order by %s \'; $sqlCalcFoundRows = \'select max(rownum) from (\'. $sql. \')\'; $sql = \'select * from (select a.*, rownum r from (\'. $sql. \') a where rownum <= 10) b where r > 0\'; // insert $sql = \'insert into %s (%s) values (%s)\'; $sqlInsertId = \'select sequ_%s.currval from %s\'; // update $sql = \'update %s set %s \'; // delete $sql = \'delete from %s %s\'; // replace $sql = \'merge into %s a using (select %s from dual where rownum < 2) b on (a.%s = b.%s) when matched then update set %s when not matched then insert (%s) values (%s)\'; // startTransaction // commitTransaction oci_commit($linkId); // rollbackTransaction oci_rollback($linkId);