如何在猫鼬中添加运算符

Question

How i can use operators like $max $min with mongoose

I tried

 User.find({Followers:max});

but that didn't work

Answer 1

You can use the .aggregate() method

db.collection.aggregate([ 
    { "$group": { 
        "_id": null,
        "max": { "$max": "$Followers" }, 
        "min": { "$min": "$Followers" } 
    }}
])

The _id should be null otherwise the query will only return max/min for each group

Answer 2

$max and $min operators will not work with .find(), you need to use .aggregate() for it to work.

    user.aggregate([ 
          { "$group": { 
                "_id": null,
                "maxfollowers": { "$max": "$Followers" }, 
                "minfollowers": { "$min": "$Followers" } 
          }}
       ])

_id field is mandatory in the $group and to find the max/min values for Followers for the entire collection not for special group it needs to be set to null otherwise if you want the result for each group you can use that field name instead of null eg

    user.aggregate([ 
      { "$group": { 
             "_id": "$name",
             "maxfollowers": { "$max": "$Followers" }, 
             "minfollowers": { "$min": "$Followers" } 
          }}
     ])