/system/database/drivers/mysql/mysql_driver.php MYSQL数据库配置器类
<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed'); /** * CodeIgniter * * An open source application development framework for PHP 5.1.6 or newer * * @package CodeIgniter * @author ExpressionEngine Dev Team * @copyright Copyright (c) 2008 - 2011, EllisLab, Inc. * @license http://codeigniter.com/user_guide/license.html * @link http://codeigniter.com * @since Version 1.0 * @filesource */ // ------------------------------------------------------------------------ /** * MySQL Database Adapter Class * * mysql 数据库的适配器类 * * Note: _DB is an extender class that the app controller * creates dynamically based on whether the active record * class is being used or not. * * 注:_DB是一个扩展类应用控制器 * 创建动态的基础上是否活动记录类正在使用与否。 * @package CodeIgniter * @subpackage Drivers * @category Database * @author ExpressionEngine Dev Team * @link http://codeigniter.com/user_guide/database/ */ class CI_DB_mysql_driver extends CI_DB { var $dbdriver = 'mysql'; //数据库类型 // The character used for escaping 用于转义字符 var $_escape_char = '`'; // clause and character used for LIKE escape sequences - not used in MySQL // 在MySQL中使用条款和字符用于LIKE转义序列 - var $_like_escape_str = ''; var $_like_escape_chr = ''; /** * Whether to use the MySQL "delete hack" which allows the number * of affected rows to be shown. Uses a preg_replace when enabled, * adding a bit more processing to all queries. * *是否使用MySQL的“删除”,它允许黑客的数量 * 受影响的行显示。 preg_replace函数使用一个启用时, * 添加更多一点的处理所有的查询。 */ var $delete_hack = TRUE; /** * The syntax to count rows is slightly different across different * database engines, so this string appears in each driver and is * used for the count_all() and count_all_results() functions. * 在不同的数行的语法略有不同 * 数据库引擎,所以这个字符串出现在每个驱动器和 * 用于count_all()和count_all_results()函数。 * */ var $_count_string = 'SELECT COUNT(*) AS '; var $_random_keyword = ' RAND()'; // database specific random keyword 数据库特定的随机关键字 // whether SET NAMES must be used to set the character set // 是否SET名称必须使用设置字符集 var $use_set_names; /** * Non-persistent database connection * 非持久性数据库连接 * @access private called by the base class 私人称为基类 * @return resource 返回资源 */ function db_connect() { //发果接口不为空 if ($this->port != '') { //拼接到hostname后面 $this->hostname .= ':'.$this->port; } //返回一个数据库链接资源 return @mysql_connect($this->hostname, $this->username, $this->password, TRUE); } // -------------------------------------------------------------------- /** * Persistent database connection * 持久数据库连接 * @access private called by the base class * @return resource */ function db_pconnect() { if ($this->port != '') { $this->hostname .= ':'.$this->port; } return @mysql_pconnect($this->hostname, $this->username, $this->password); } // -------------------------------------------------------------------- /** * Reconnect * 重新连接 * * Keep / reestablish the db connection if no queries have been * sent for a length of time exceeding the server's idle timeout * 保持/重新建立数据库连接,如果没有查询 * 发送的时间长度超过服务器的空闲超时 * @access public * @return void */ function reconnect() { //mysql_ping($this->conn_id) === false //mysql_ping 检查与服务端的连接是否正常检查与服务端的连接是否正常。连接断开时,如果自动重新连接功能未被禁用,则尝试重新连接服务器。该函数可被客户端用来检测闲置许久以后,与服务端的连接是否关闭,如有需要,则重新连接。 if (mysql_ping($this->conn_id) === FALSE) //如果链接已经也断开 { $this->conn_id = FALSE; //将链接资源设置为false } } // -------------------------------------------------------------------- /** * Select the database * 选择数据库 * * @access private called by the base class * @return resource */ function db_select() { return @mysql_select_db($this->database, $this->conn_id); } // -------------------------------------------------------------------- /** * Set client character set * 设置客户端的字符编码 * * @access public * @param string * @param string * @return resource */ function db_set_charset($charset, $collation) { //如果没有设置字符 if ( ! isset($this->use_set_names)) { // mysql_set_charset() requires PHP >= 5.2.3 and MySQL >= 5.0.7, use SET NAMES as fallback // 在指定的php版本和mysql版本才能设置mysql_set_charset()函数 $this->use_set_names = (version_compare(PHP_VERSION, '5.2.3', '>=') && version_compare(mysql_get_server_info(), '5.0.7', '>=')) ? FALSE : TRUE; } if ($this->use_set_names === TRUE) { //合适的版本,设置 set names return @mysql_query("SET NAMES '".$this->escape_str($charset)."' COLLATE '".$this->escape_str($collation)."'", $this->conn_id); } else { return @mysql_set_charset($charset, $this->conn_id); } } // -------------------------------------------------------------------- /** * Version number query string * 取得版本信息 * @access public * @return string */ function _version() { return "SELECT version() AS ver"; } // -------------------------------------------------------------------- /** * Execute the query * 执行查询 * * @access private called by the base class * @param string an SQL query * @return resource */ function _execute($sql) { $sql = $this->_prep_query($sql); return @mysql_query($sql, $this->conn_id); } // -------------------------------------------------------------------- /** * Prep the query * 准备查询 * * If needed, each database adapter can prep the query string * 如果需要,每个数据库适配器可以预先准备的查询字符串 * * @access private called by execute() * @param string an SQL query * @return string */ function _prep_query($sql) { // "DELETE FROM TABLE" returns 0 affected rows This hack modifies // the query so that it returns the number of affected rows // “DELETE FROM表”,返回受影响的行黑客修改 // 查询,以便它返回受影响的行数 // delete hack=破解 if ($this->delete_hack === TRUE) { //如果字符串是为什 delete + FROM 一些字符串 if (preg_match('/^\s*DELETE\s+FROM\s+(\S+)\s*$/i', $sql)) { //替换为delete from 1 where 1=1 $sql = preg_replace("/^\s*DELETE\s+FROM\s+(\S+)\s*$/", "DELETE FROM \\1 WHERE 1=1", $sql); } } return $sql; } // -------------------------------------------------------------------- /** * Begin Transaction * 开始交易 * * @access public * @return bool */ function trans_begin($test_mode = FALSE) { if ( ! $this->trans_enabled) { return TRUE; } // When transactions are nested we only begin/commit/rollback the outermost ones // 当事务被嵌套,我们才开始/提交/回滚最外层的 if ($this->_trans_depth > 0) { return TRUE; } // Reset the transaction failure flag. // If the $test_mode flag is set to TRUE transactions will be rolled back // even if the queries produce a successful result. // 复位的交易失败标志。 // 如果$ TEST_MODE标志设置为TRUE交易将回滚 // 即使查询产生一个成功的结果。 $this->_trans_failure = ($test_mode === TRUE) ? TRUE : FALSE; //开始事务处理 //set AUTOCOMMIT=0 禁止自动提交 $this->simple_query('SET AUTOCOMMIT=0'); $this->simple_query('START TRANSACTION'); // can also be BEGIN or BEGIN WORK 也可以开始或开始工作 return TRUE; } // -------------------------------------------------------------------- /** * Commit Transaction * commit 事务 * * @access public * @return bool */ function trans_commit() { if ( ! $this->trans_enabled) { return TRUE; } // When transactions are nested we only begin/commit/rollback the outermost ones // 当事务被嵌套,我们才开始/提交/回滚最外层的 if ($this->_trans_depth > 0) { return TRUE; } //COMMIT 确定一个事务 $this->simple_query('COMMIT'); //SET AUTOCOMMIT=1 开启自动提交 $this->simple_query('SET AUTOCOMMIT=1'); return TRUE; } // -------------------------------------------------------------------- /** * Rollback Transaction * 回滚事务 * * @access public * @return bool */ function trans_rollback() { if ( ! $this->trans_enabled) { return TRUE; } // When transactions are nested we only begin/commit/rollback the outermost ones if ($this->_trans_depth > 0) { return TRUE; } //判断当前操作失败时回滚 //ROLLBACK 判断当前操作失败时回滚 $this->simple_query('ROLLBACK'); $this->simple_query('SET AUTOCOMMIT=1'); //set AUTOCOMMIT =1; 开启自动提交 return TRUE; } // -------------------------------------------------------------------- /** * Escape String * 转义字符串 * @access public * @param string * @param bool whether or not the string will be used in a LIKE condition * @return string 是否该字符串将被用于在LIKE条件 */ function escape_str($str, $like = FALSE) { //如果是数组 循环进行递归操作 if (is_array($str)) { foreach ($str as $key => $val) { $str[$key] = $this->escape_str($val, $like); } return $str; } //判断是存存在mysql_real_escape_string函数 //mysql_real_escape_string() 函数转义sql语句中使用的字符串的特殊字符 /* 下列字符受影响: \x00 \n \r \ ' " \x1a 如果成功,则该函数返回被转义的字符串。如果失败,则返回 false。 * */ if (function_exists('mysql_real_escape_string') AND is_resource($this->conn_id)) { $str = mysql_real_escape_string($str, $this->conn_id); } //mysql_escape_string() PHP 4 >= 4.0.3, PHP 5, 注意:在PHP5.3中已经弃用这种方法,不推荐使用 elseif (function_exists('mysql_escape_string')) { $str = mysql_escape_string($str); } else { $str = addslashes($str); //直接用addslashes操作 } // escape LIKE condition wildcards // 逃离LIKE条件通配符 if ($like === TRUE) { $str = str_replace(array('%', '_'), array('\\%', '\\_'), $str); } return $str; } // -------------------------------------------------------------------- /** * Affected Rows * 受影响的列 mysql_sffected_rows($this->conn_id) * @access public * @return integer */ function affected_rows() { return @mysql_affected_rows($this->conn_id); } // -------------------------------------------------------------------- /** * Insert ID * 最提插入的列id, 也就是取得最近一次插入数据的id号 mysql_insert_id($this->conn_id) * @access public * @return integer */ function insert_id() { return @mysql_insert_id($this->conn_id); } // -------------------------------------------------------------------- /** * "Count All" query * 获取所有查询 * * Generates a platform-specific query string that counts all records in * the specified database * 生成一个平台特定的查询字符串中的所有记录计数指定的数据库 * @access public * @param string * @return string */ function count_all($table = '') { if ($table == '') { return 0; } // SELECT COUNT(*) AS numrows from tableName; $query = $this->query($this->_count_string . $this->_protect_identifiers('numrows') . " FROM " . $this->_protect_identifiers($table, TRUE, NULL, FALSE)); //如果记录数为0 if ($query->num_rows() == 0) { return 0; } $row = $query->row(); //取得一行数据 $this->_reset_select(); //重置查询条件 return (int) $row->numrows; //返回记录总数 } // -------------------------------------------------------------------- /** * List table query * 清单表查询 * * Generates a platform-specific query string so that the table names can be fetched * 生成一个特定于平台的查询字符串,以便可以获取表名 * * @access private * @param boolean * @return string */ function _list_tables($prefix_limit = FALSE) { //取得数据库的所有表信息 $sql = "SHOW TABLES FROM ".$this->_escape_char.$this->database.$this->_escape_char; //like 指定表名的数据 //SHOW tables FROM databasename like '%TB%' if ($prefix_limit !== FALSE AND $this->dbprefix != '') { $sql .= " LIKE '".$this->escape_like_str($this->dbprefix)."%'"; } return $sql; } // -------------------------------------------------------------------- /** * Show column query * 显示查询列信息 * * Generates a platform-specific query string so that the column names can be fetched * 生成一个特定于平台的查询字符串,所以也可以获取列名 * * @access public * @param string the table name * @return string */ function _list_columns($table = '') { //show COLUMNS FROM tablename return "SHOW COLUMNS FROM ".$this->_protect_identifiers($table, TRUE, NULL, FALSE); } // -------------------------------------------------------------------- /** * Field data query * 现场数据查询 * Generates a platform-specific query so that the column data can be retrieved * 所以也可以检索列数据,生成特定平台查询 * @access public * @param string the table name * @return object */ function _field_data($table) { return "DESCRIBE ".$table; } // -------------------------------------------------------------------- /** * The error message string * 该错误消息字符串 * @access private * @return string */ function _error_message() { return mysql_error($this->conn_id); } // -------------------------------------------------------------------- /** * The error message number * 该错误消息的数值 * * @access private * @return integer */ function _error_number() { return mysql_errno($this->conn_id); } // -------------------------------------------------------------------- /** * Escape the SQL Identifiers * 逃离SQL标识符 * This function escapes column and table names * 此功能逃脱列和表名 * @access private * @param string * @return string */ function _escape_identifiers($item) { //如果为空,直接返回 if ($this->_escape_char == '') { return $item; } // foreach ($this->_reserved_identifiers as $id) { //在teim中存在.加上$id的话, if (strpos($item, '.'.$id) !== FALSE) { // ` + `. // a.name; //`a`.name $str = $this->_escape_char. str_replace('.', $this->_escape_char.'.', $item); // remove duplicates if the user already included the escape // 删除重复,如果用户已经逃逸 // [`]+ 如果出现多次,那么`进行替换 return preg_replace('/['.$this->_escape_char.']+/', $this->_escape_char, $str); } } //如果item中没有. if (strpos($item, '.') !== FALSE) { // a.name //`a`.`name` $str = $this->_escape_char.str_replace('.', $this->_escape_char.'.'.$this->_escape_char, $item).$this->_escape_char; } else { $str = $this->_escape_char.$item.$this->_escape_char; } // remove duplicates if the user already included the escape // 删除重复,如果用户已经逃逸 return preg_replace('/['.$this->_escape_char.']+/', $this->_escape_char, $str); } // -------------------------------------------------------------------- /** * From Tables * * This function implicitly groups FROM tables so there is no confusion * about operator precedence in harmony with SQL standards * 此功能隐含团队从表所以没有混乱 * 运算符优先级在和谐与SQL标准 * * @access public * @param type * @return type */ function _from_tables($tables) { if ( ! is_array($tables)) { $tables = array($tables); } return '('.implode(', ', $tables).')'; } // -------------------------------------------------------------------- /** * Insert statement * insert 语句 * * Generates a platform-specific insert string from the supplied data * 从所提供的数据,生成特定平台插入字符串 * * @access public * @param string the table name * @param array the insert keys * @param array the insert values * @return string */ function _insert($table, $keys, $values) { return "INSERT INTO ".$table." (".implode(', ', $keys).") VALUES (".implode(', ', $values).")"; } // -------------------------------------------------------------------- /** * Replace statement * 替换语句 * * Generates a platform-specific replace string from the supplied data * 从所提供的数据,生成一个特定于平台的替换字符串 * * @access public * @param string the table name * @param array the insert keys * @param array the insert values * @return string */ function _replace($table, $keys, $values) { return "REPLACE INTO ".$table." (".implode(', ', $keys).") VALUES (".implode(', ', $values).")"; } // -------------------------------------------------------------------- /** * Insert_batch statement * 插入批量语句 * * Generates a platform-specific insert string from the supplied data * 从所提供的数据,生成特定平台插入字符串 * * @access public * @param string the table name * @param array the insert keys * @param array the insert values * @return string */ function _insert_batch($table, $keys, $values) { return "INSERT INTO ".$table." (".implode(', ', $keys).") VALUES ".implode(', ', $values); } // -------------------------------------------------------------------- /** * Update statement * 更新语句 * * Generates a platform-specific update string from the supplied data * 从所提供的数据,生成特定平台的更新字符串 * * @access public * @param string the table name * @param array the update data * @param array the where clause * @param array the orderby clause * @param array the limit clause * @return string */ function _update($table, $values, $where, $orderby = array(), $limit = FALSE) { //对$values的值进行拼接 foreach ($values as $key => $val) { $valstr[] = $key . ' = ' . $val; } //如果有 limit $limit = ( ! $limit) ? '' : ' LIMIT '.$limit; //如明 order by $orderby = (count($orderby) >= 1)?' ORDER BY '.implode(", ", $orderby):''; //开始拼接update 语句 $sql = "UPDATE ".$table." SET ".implode(', ', $valstr); //如果有条件,where $sql .= ($where != '' AND count($where) >=1) ? " WHERE ".implode(" ", $where) : ''; $sql .= $orderby.$limit; return $sql; } // -------------------------------------------------------------------- /** * Update_Batch statement * 批量更新语句 * * Generates a platform-specific batch update string from the supplied data * 从所提供的数据,生成一个特定于平台的批量更新字串 * * @access public * @param string the table name * @param array the update data * @param array the where clause * @return string */ function _update_batch($table, $values, $index, $where = NULL) { $ids = array(); //如果$where条件不为空,那么用空格拼接成字符串 后面加上AND $where = ($where != '' AND count($where) >=1) ? implode(" ", $where).' AND ' : ''; //开始循环需要更新的值 foreach ($values as $key => $val) { $ids[] = $val[$index]; //取得$val中指定的索引值 //取得$val数组中的所有key值数组,并循环 foreach (array_keys($val) as $field) { //拼接成 WHEN......THEN...... //总算弄明白case when then 什么意思了,跟php 中的switch case差不多 if ($field != $index) { $final[$field][] = 'WHEN '.$index.' = '.$val[$index].' THEN '.$val[$field]; } } } $sql = "UPDATE ".$table." SET "; $cases = ''; //整个这个循环有点没弄清楚什么情 foreach ($final as $k => $v) { $cases .= $k.' = CASE '."\n"; foreach ($v as $row) { $cases .= $row."\n"; } $cases .= 'ELSE '.$k.' END, '; } $sql .= substr($cases, 0, -2); $sql .= ' WHERE '.$where.$index.' IN ('.implode(',', $ids).')'; return $sql; } // -------------------------------------------------------------------- /** * Truncate statement * 截断语句 * * Generates a platform-specific truncate string from the supplied data * If the database does not support the truncate() command * This function maps to "DELETE FROM table" * 从所提供的数据,生成一个特定于平台的截断字符串 * 如果数据库不支持的截断()命令。 * 此功能映射到“DELETE FROM表” * @access public * @param string the table name * @return string */ function _truncate($table) { return "TRUNCATE ".$table; //TRUNCATE talbename 是sql中的一个删除数据表内容的语句 } // -------------------------------------------------------------------- /** * Delete statement * * Generates a platform-specific delete string from the supplied data * 从所提供的数据,生成一个特定于平台的删除字符串 * * @access public * @param string the table name * @param array the where clause * @param string the limit clause * @return string */ function _delete($table, $where = array(), $like = array(), $limit = FALSE) { $conditions = ''; if (count($where) > 0 OR count($like) > 0) { $conditions = "\nWHERE "; $conditions .= implode("\n", $this->ar_where); if (count($where) > 0 && count($like) > 0) { $conditions .= " AND "; } $conditions .= implode("\n", $like); } $limit = ( ! $limit) ? '' : ' LIMIT '.$limit; return "DELETE FROM ".$table.$conditions.$limit; } // -------------------------------------------------------------------- /** * Limit string * * Generates a platform-specific LIMIT clause * 生成特定平台的限制条款 * @access public * @param string the sql query string * @param integer the number of rows to limit the query to * @param integer the offset value * @return string */ function _limit($sql, $limit, $offset) { if ($offset == 0) { $offset = ''; } else { $offset .= ", "; } return $sql."LIMIT ".$offset.$limit; } // -------------------------------------------------------------------- /** * Close DB Connection * 关闭数据库链接 * @access public * @param resource * @return void */ function _close($conn_id) { @mysql_close($conn_id); } } /* End of file mysql_driver.php */ /* Location: ./system/database/drivers/mysql/mysql_driver.php */