mongoDB,聚合中如何写判断if else

Question

db.areas.aggregate([
  {
    $match:{
      'code':'130',
      'level':'level1'
    }
  },
    {
      $lookup:{
        'from':'users',
        'localField':'_id',
        'foreignField':'area.code',//这里想写个判断 该怎么写，
                                               //比如level是’level1' 就‘area.code1',
                                               //level是’level2' 就‘area.code2',
                                               //level是’level3' 就‘area.code3
        'as':'xxx'
      }
    }
  ])

Answer 1

下面这篇文章,希望能给你带来帮助
https://blog.csdn.net/weixin_39580031/article/details/122727009