//获取指定多行多列，二维,,对象 【select】
         $names = '';
         $names = DB::table('student')->whereRaw('id > ? and age < ?',[1,100])->select('id','name','age')->get();
         var_dump($names);
         echo "<br>";

        //获取指定单行，一维,,对象 【find】
        $names = '';
        $names = DB::table('student')->whereRaw('id > ? and age < ?',[1,100])->select('id','name','age')->first();
        var_dump($names);
        echo "ceshi";
        echo "<br>";

        //获取指定列值，返回字符串【getField】
        $names = DB::table('student')->whereRaw('id >= ? and age < ?',[1,100])->value('name');
        var_dump($names);   //  string(3) "bob"
        echo "<br>";

        //获取指定name单列，返回一维数组【getField,true】
        $names = '';
        $names = DB::table('student')->whereRaw('id >= ? and age < ?',[1,100])->pluck('name');
        var_dump($names);
        echo "<br>";
        var_dump(json_encode($names,true));//  array "["Alice"]"