我是 mongo 的新手,正在努力应对以下问题。我有 2 个集合,结构如下。对于我的一生,我不知道如何对学校收藏进行 $lookup。阅读其他帖子,我肯定使用 ObjectId 作为参考以及外部字段。
下面是我的结构:
Alumni:
{
"_id": "john",
"items": [
{
"name": "John",
"items": [
{
"school": ObjectId("56de35ab520fc05b2fa3d5e4"),
"grad": true
},
{
"school": ObjectId("56de35ab520fc05b2fa00000"),
"grad": false
}
]
},
{
"name": "Johnny"
// notice no nested items, this doc should still be included in result
},
{
"name": "Jon",
"items": [
{
"school": ObjectId("56de35ab520fc05b2fa11111"),
"grad": false
}
]
}
]
}
Schools
{
_id: ObjectId("56de35ab520fc05b2fa3d5e4"),
name: "Some University",
street: "ABC Boulevard"
}
我想要得到什么:
{
"_id": "john",
"items": [
{
"name": "John",
"items": [
{
"school": ObjectId("56de35ab520fc05b2fa3d5e4"),
"grad": true,
"schoolInfo": {
_id: ObjectId("56de35ab520fc05b2fa3d5e4"),
name: "Some University",
street: "ABC Boulevard"
}
},
{
"school": ObjectId("56de35ab520fc05b2fa00000"),
"grad": true,
"schoolInfo": {
_id: ObjectId("56de35ab520fc05b2fa00000"),
name: "Another University",
street: "123 Boulevard"
}
}
]
},
{
name: "Johnny"
},
{
"name": "Jon",
"items": [
{
"school": ObjectId("56de35ab520fc05b2fa11111"),
"grad": true,
"schoolInfo": {
_id: ObjectId("56de35ab520fc05b2fa11111"),
name: "Some University",
street: "ABC Boulevard"
}
}
]
}
]
}
我尝试过的查询无济于事:
db.alumni.aggregate([
{$match: {_id: 'john'}},
{$lookup: {
from: 'schools',
localField: 'items.items.school',
foreignField: '_id',
as: 'schoolInfo'}}
])
任何帮助将不胜感激!