如何明智地检索数组值索引

Question

如何在MongoDB中以索引方式检索数组值？在下面的查询中，我想要Computers作为答案：

> db.customers.find({}, { likes : { $slice: 1}}).pretty()
{
        "_id" : ObjectId("57709662a93160be074de74a"),
        "name" : "John",
        "age" : "40",
        "likes" : [
                "Computers"
        ]
}

Answer 1

这就是你要找的东西

db.customers.aggregate([{$project:{_id:0,selected:{$slice:["$likes", 1]}}},{$unwind:"$selected"}]);