thinkphp 数据访问

<?php
namespace Admin\Controller;
use Think\Controller;
class MainController extends Controller
{
    public function showList()
    {
        echo "大苹果商城";
    }

    public function test()
    {
        //数据访问
        //造模型对象
        $nation = D("Nation");

        //查询
        //$a = $nation->select(); //查所有，返回关联数组
        //$a = $nation->select("n001,n002,n003"); //通过主键查
        //$a = $nation->find("n002"); //查一条数据

        连贯操作
        $a = $nation->where("name=‘汉族‘ or name=‘回族‘")->select(); //加条件
        $a = $nation->table("Info")->select(); //切换表
        $a = $nation->field("name")->select(); //查询指定字段
        $a = $nation->order("code desc")->select(); //排序
        $a = $nation->limit(3,3)->select(); //分页
        $a = $nation->page(3,3)->select(); //分页
        $a = $nation->table("Car")->field("Brand,avg(Price)")->group("Brand")->select(); //分组
        $a = $nation->table("Car")->field("Brand,avg(Price)")->group("Brand")->having("avg(Price)>50")->select();

        $a = $nation->alias(‘a‘)->field("b.Code as ‘code‘,b.Name as ‘name‘,a.name as ‘民族‘")->join("Info b on a.Code=b.Nation")->select();

        $a = $nation->table("car")->distinct(true)->field("brand")->select();

        $a = $nation->where("code=‘n003‘")->getField("name"); //获取某一列的值

        $a = $nation->table("car")->sum(Price);
        var_dump($a);

        //$sql = "update nation set name=‘矮人族‘ where code=‘n001‘";
        //$a = $nation->query($sql); //执行查询
        //$a = $nation->execute($sql); //执行其他操作
        //var_dump($a);

    }
}