MongoDB小结20 - find【查询条件$size】

size可以获得指定数组长度的文档

db.user.find({"fruit":{"$size":3}},{"_id":0})
{ "fruit" : [ "apple", "banana", "cherry" ] }
{ "fruit" : [ "apple", "banana", "pear" ] }
{ "fruit" : [ "apple", "watermelon", "pear" ] }