moodle笔记之-数据库操作

具体详见：https://www.cnblogs.com/lichihua/p/5706285.html

<?php

require_once('../config.php'); // config.php under root folder

require_once($CFG->dirroot .'/course/lib.php');
require_once($CFG->libdir .'/filelib.php');

//redirect_if_major_upgrade_required();

参数详解

//看到有多少匹配给定标准的记录
//①count_records：$DB->count_records($table, array $conditions=null)

//统计函数相当于：select count(*) from mdl_user; echo $DB->count_records('user').'<br><br>'; // 查询有多少用户

// ②$DB->count_records_select($table, $select, array $params=null, $countitem="COUNT('x')")

// 注意：COUNT('x')等同于COUNT(*) echo $DB->count_records_select('user', 'firstname=?', array('同学'),"COUNT('x')").'

数据库结构操作：

https://docs.moodle.org/dev/Data_definition_API

function xmldb_xxxx_upgrade {
 
    global $DB;
 
    $dbman = $DB->get_manager(); // loads ddl manager and xmldb classes
 
    /// Your upgrade code goes here
}

操作数据表：

/// To detect if one table exists:
    $dbman->table_exists($table)
 
/// To create one table:
    $dbman->create_table($table, $continue=true, $feedback=true)
 
/// To drop one table:
    $dbman->drop_table($table, $continue=true, $feedback=true)
 
/// To rename one table:
    $dbman->rename_table($table, $newname, $continue=true, $feedback=true)

操作数据字段：

/// To detect if one field exists:
    $dbman->field_exists($table, $field)
 
/// To create one field:
    $dbman->add_field($table, $field, $continue=true, $feedback=true)
 
/// To drop one field:
    $dbman->drop_field($table, $field, $continue=true, $feedback=true)
 
/// To change the type of one field:
    $dbman->change_field_type($table, $field, $continue=true, $feedback=true)
 
/// To change the precision of one field:
    $dbman->change_field_precision($table, $field, $continue=true, $feedback=true)
 
/// To change the signed/unsigned status of one field:
    $dbman->change_field_unsigned($table, $field, $continue=true, $feedback=true)
 
/// To make one field nullable or not:
    $dbman->change_field_notnull($table, $field, $continue=true, $feedback=true)
 
/// To drop one enum (check constraint) from one field:
/// (note this function will be only available in Moodle 2.0 as it's needed
/// to drop any enum existing in previous Moodle releases). Will be out in Moodle 2.1
    $dbman->drop_enum_from_field($table, $field, $continue=true, $feedback=true)
 
/// To change the default value of one field:
    $dbman->change_field_default($table, $field, $continue=true, $feedback=true)
 
/// To rename one field:
    $dbman->rename_field($table, $field, $newname, $continue=true, $feedback=true)

操作索引：

/// To detect if one index exists:
    $dbman->index_exists($table, $index)
 
/// To return the name of one index in DB:
    $dbman->find_index_name($table, $index)
 
/// To add one index:
    $dbman->add_index($table, $index, $continue=true, $feedback=true)
 
/// To drop one index:
    $dbman->drop_index($table, $index, $continue=true, $feedback=true)