PHP代码：

``` php

use think\facade\Db;

​

$map0 = [

    ['userid', '=', '1']

];

$map1 = [

    ['username', '=', '1']

];

$map2 = [

    ['username', '=', '2']

];    

$db = Db::table('vt_user');

$db->where($map0)->where(function($query)use($map1,$map2){

    $query->whereOr([$map1,$map2]);

})->select();

echo $db->getLastSql();exit;

```

输出：

``` 

SELECT * FROM `vt_user` WHERe `userid` = 1 AND ( ( `username` = '1' ) OR ( `username` = '2' ) )

```