在猫鼬中按日期分组

Question

这是我的约会收藏

{ _id: ObjectId("518ee0bc9be1909012000002"), date: ISODate("2013-05-13T22:00:00Z"), patient:"John" }

{ _id: ObjectId("518ee0bc9be1909012000002"), date: ISODate("2013-05-13T22:00:00Z"), patient:"alex" }

{ _id: ObjectId("518ee0bc9be1909012000002"), date: ISODate("2013-05-13T22:00:00Z"), patient:"sara" }

我怎样才能得到这样的结果

{date: ISODate("2013-05-13T22:00:00Z"),
patients:["John","alex","sara"] }

我试试这个

Appointments.aggregate([
{
$group: {
_id: '$date'
}
}
], function(err, doc) {
return console.log(JSON.stringify(doc));
});

请帮忙

Answer 1

使用$push聚合运算符将patients数组组装到$group中：

Appointments.aggregate([
    {$group: {_id: '$date', patients: {$push: '$patient'}}},
    {$project: {date: '$_id', patients: 1, _id: 0}}
], ...)

在您的后续问题中包含患者 ID：

Appointments.aggregate([
    {$group: {_id: '$date', patients: {$push: {
        patient: '$patient'
        _id: '$_id'
    }}}},
    {$project: {date: '$_id', patients: 1, _id: 0}}
], ...)