/system/database/drivers/mysql/mysql_forge.php MYSQL数据库实工具类
<?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 Forge Class * mysql 实用工具类 * * @category Database * @author ExpressionEngine Dev Team * @link http://codeigniter.com/user_guide/database/ */ class CI_DB_mysql_forge extends CI_DB_forge { /** * Create database * 创建数据库 create database databasename * @access private * @param string the database name * @return bool */ function _create_database($name) { return "CREATE DATABASE ".$name; } // -------------------------------------------------------------------- /** * Drop database * 清空数据库 drop database databasename * @access private * @param string the database name * @return bool */ function _drop_database($name) { return "DROP DATABASE ".$name; } // -------------------------------------------------------------------- /** * Process Fields * * @access private * @param mixed the fields * @return string */ function _process_fields($fields) { $current_field_count = 0; //当前字段的总数 $sql = ''; //开始循环字段 foreach ($fields as $field=>$attributes) { // Numeric field names aren't allowed in databases, so if the key is // numeric, we know it was assigned by PHP and the developer manually // entered the field information, so we'll simply add it to the list // 数字字段名不允许在数据库中,因此,如果关键是数字,我们知道它是PHP和开发商手动分配 // 输入的字段信息,所以我们只需将其添加到列表 //如果是数字,直接放在$sql. if (is_numeric($field)) { $sql .= "\n\t$attributes"; } else { //array_change_key_case() 返回字符串键名全为小写或大写的数组 $attributes = array_change_key_case($attributes, CASE_UPPER); $sql .= "\n\t".$this->db->_protect_identifiers($field); //判断在$attributes 数组中是否存在NAME这个键 值名称 if (array_key_exists('NAME', $attributes)) { //取得NAME这个键 值 $sql .= ' '.$this->db->_protect_identifiers($attributes['NAME']).' '; } //判断是否存在TYPE这个键 值名称 if (array_key_exists('TYPE', $attributes)) { // $sql .= ' '.$attributes['TYPE']; //取CONSTRAINT //constraint //consttrint //CONSTTRINT子句是指限制和索引相似,虽然限制也能被用于建立的另一个表的关联,用ALTER TABLE // 和CREATE TABLE语句中的CONSTRAINT 子句来建立或删除条件,constraint子句可以分为两种类型,第一种 // 是在单一字段上创建条件,第二种是在一个以上的字段上创建条件 if (array_key_exists('CONSTRAINT', $attributes)) { switch ($attributes['TYPE']) { case 'decimal': //双精度 case 'float': //浮点型 case 'numeric': //整型 $sql .= '('.implode(',', $attributes['CONSTRAINT']).')'; break; case 'enum': //enum case 'set': //set $sql .= '("'.implode('","', $attributes['CONSTRAINT']).'")'; break; default: $sql .= '('.$attributes['CONSTRAINT'].')'; } } } if (array_key_exists('UNSIGNED', $attributes) && $attributes['UNSIGNED'] === TRUE) { $sql .= ' UNSIGNED'; } //default 默认值 if (array_key_exists('DEFAULT', $attributes)) { $sql .= ' DEFAULT \''.$attributes['DEFAULT'].'\''; } //是否为null if (array_key_exists('NULL', $attributes) && $attributes['NULL'] === TRUE) { $sql .= ' NULL'; } else { $sql .= ' NOT NULL'; } //是否为自增长 //auto_increment if (array_key_exists('AUTO_INCREMENT', $attributes) && $attributes['AUTO_INCREMENT'] === TRUE) { $sql .= ' AUTO_INCREMENT'; } } // don't add a comma on the end of the last field 不上的最后一个字段的末尾添加一个逗号 if (++$current_field_count < count($fields)) { $sql .= ','; } } return $sql; } // -------------------------------------------------------------------- /** * Create Table * 创建数据表 * * @access private * @param string the table name 表名 * @param mixed the fields 字段 * @param mixed primary key(s) // * @param mixed key(s) * @param boolean should 'IF NOT EXISTS' be added to the SQL 判断表是否存在 * @return bool */ function _create_table($table, $fields, $primary_keys, $keys, $if_not_exists) { $sql = 'CREATE TABLE '; if ($if_not_exists === TRUE) { $sql .= 'IF NOT EXISTS '; } $sql .= $this->db->_escape_identifiers($table)." ("; $sql .= $this->_process_fields($fields); //字段进行处理 //如果大于0 if (count($primary_keys) > 0) { // $key_name = $this->db->_protect_identifiers(implode('_', $primary_keys)); $primary_keys = $this->db->_protect_identifiers($primary_keys); $sql .= ",\n\tPRIMARY KEY ".$key_name." (" . implode(', ', $primary_keys) . ")"; } //索引值吗? if (is_array($keys) && count($keys) > 0) { foreach ($keys as $key) { if (is_array($key)) { $key_name = $this->db->_protect_identifiers(implode('_', $key)); $key = $this->db->_protect_identifiers($key); } else { $key_name = $this->db->_protect_identifiers($key); $key = array($key_name); } $sql .= ",\n\tKEY {$key_name} (" . implode(', ', $key) . ")"; } } //设置数据库的编码 //default character set char_set collate dbcollat $sql .= "\n) DEFAULT CHARACTER SET {$this->db->char_set} COLLATE {$this->db->dbcollat};"; return $sql; } // -------------------------------------------------------------------- /** * Drop Table * 清空表 * * @access private * @return string drop table if exists */ function _drop_table($table) { return "DROP TABLE IF EXISTS ".$this->db->_escape_identifiers($table); } // -------------------------------------------------------------------- /** * Alter table query * ALTER TABLE查询 * * Generates a platform-specific query so that a table can be altered * Called by add_column(), drop_column(), and column_alter(), * 生成一个特定于平台的查询,以便可以改变一个表 * 由add_column(),drop_column(),column_alter()调用, * * @access private * @param string the ALTER type (ADD, DROP, CHANGE) * @param string the column name * @param array fields * @param string the field after which we should add the new field * @return object */ function _alter_table($alter_type, $table, $fields, $after_field = '') { //ALTER TABLE 语句用于在已有的表中添加,修改或删除列 $sql = 'ALTER TABLE '.$this->db->_protect_identifiers($table)." $alter_type "; // DROP has everything it needs now. // DROP它现在需要的一切。 if ($alter_type == 'DROP') { return $sql.$this->db->_protect_identifiers($fields); } $sql .= $this->_process_fields($fields); if ($after_field != '') { $sql .= ' AFTER ' . $this->db->_protect_identifiers($after_field); } return $sql; } // -------------------------------------------------------------------- /** * Rename a table * 重命名表名 * * Generates a platform-specific query so that a table can be renamed * 生成一个特定于平台的查询,以便可以重命名的表 * @access private * @param string the old table name * @param string the new table name * @return string rename to */ function _rename_table($table_name, $new_table_name) { $sql = 'ALTER TABLE '.$this->db->_protect_identifiers($table_name)." RENAME TO ".$this->db->_protect_identifiers($new_table_name); return $sql; } } /* End of file mysql_forge.php */ /* Location: ./system/database/drivers/mysql/mysql_forge.php */