// 增
	public function insert(){
	    $data = array(
	        "username"=>"user121",
            "password"=>"123456"
        );
	    $code=Db::table('user')->insertGetId($data);
	    dump($code);
	}
	
	// 删
	public function delete(){
        $where = array(
            'id' =>17
        );
//		$code=Db::table('user')->where('id>38 and id<40')->delete();
		$code=Db::table('user')->where($where)->delete();
		dump($code);
	}
	
	// 改
	public function update(){
	    $data = array(
	        'username' => 'fsadfsaf'
        );
        $where = array(
            'id' =>18
        );
		$code=Db::table('user')->where($where)->update($data);
		dump($code);
	}
	
	// 查
	public function select(Request $request){
	    $where = 'id < 18';
	    $field = 'username,password';
		//查询所有数据
		 $data=Db::table('user')->field($field)->where($where)->select();
        dump($data);
}