MongoDB 查询 （两个字段差值作为条件查询）

Question

字段

• name string
• x int
• y int

表记录

name	x	y
jhon	1	2
lily	2	1
gan	3	2

查询结果

查询所有 x > y 的所有 name

Answer 1

db.collections.find({'$where': "this.x > this.y"}, {'name': 1})

Answer 2

This way, you can also sort by the difference between x and y

db.collection.aggregate(
    [  
      {
        $project : {
           _id: '$name',
           val: { $subtract : [ "$x", "$y" ] }，
           x: '$x',
           y: '$y'
        }
      },
      {$match: {val: {$gt: 0}}},
      {$sort: { val: -1 }}
   ]
)