tp3.2用法

        $map = array();
        $keyword = I('get.keyword');        //接收到keyword
        if (isset($keyword)) {     //keword是否存在
            $map['name'] = array('like', '%' . $keyword . '%');  //模糊搜索
        }
        $Product = D("Product");        //使用D方法
        $products = $Product->relation(true)->where($map)->order('sort_order desc')->select();   //

tp5.1用法1

if($_GET){
            $keyword = $_GET['keyword'];
            if (isset($keyword) && $keyword != ''){
                $tags = Db::name('tag')->where('name','like','%'.$keyword.'%')->order('id', 'desc')->paginate(3);
            }
        }else {
            $tags = Db::name('tag')->order('id', 'desc')->paginate(3);
        }
        $this->assign(compact('tags'));
        return $this->fetch();

tp5.1用法2

 $where = function ($query) use ($request) {
            //按商品名称
            if ($request->name and $request->name != ' ') {
                $search = "%" . $request->name . "%";
                $query->where('title', 'like', $search);
            }

        };
        $adverts = Db::table('adverts')->alias('a')
            ->field('a.*,a.id as aid, b.*')
            ->join('photo b', 'a.photo_id = b.id')->where($where)
            ->order('sort_order', 'desc')->paginate(3);  //这是jion关联
        return success_json($adverts, '查询成功!');  //这是个助手函数

laravel 5.8用法

模型当中定义静态方法，然后控制器调用

    static function all_products(Request $request)
    {
        $where = function ($query) use ($request) {   //固定写法
            //关键字查询
            if ($request->has('keyword') && $request->keyword != '') {   // 关键此存在存在且不为空则执行
                //定义模糊查询
                $search = "%" . $request->keyword . "%";
                $query->where('name', 'like', $search);
            }
            //分类查询
            if ($request->has('category_id') && $request->category_id != '-1') {
                $product_ids = CategoryProduct::where('category_id', $request->category_id)
                    ->pluck('product_id');
//                $product_ids = \DB::table('category_product')
//                    ->where('category_id', $request->category_id)->pluck('product_id');
                $query->where('id', $product_ids);
            }
          
            if ($request->is_new && $request->is_new != '') {
                $query->where('is_new', $request->is_new);
            }
            if ($request->has('created_at') and $request->created_at != '') {
                $time = explode("~", $request->created_at);   //把字符串变成数组用explode用~隔开
                $start = $time[0] . ' 00:00:00';
                $end = $time[1] . ' 23:59:59';
                $query->whereBetween('created_at', [$start, $end]);                      //用wherebetween表示在他们之间
            }


        };
        $products = Product::with('categories', 'brand')->where($where)->orderBy('sort')
            ->paginate(6);
        return $products;
    }