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[英]Get the count of other collection data from the array based on id Mongodb
[英]get _id based on value from a collection for a array and insert in mongodb collection
輸入:
[{"gradeName":1,"sectionName":"a","maximumStudents":12},{"gradeName":2,"sectionName":"b","maximumStudents":13}]
在mongodb中如何從兩個集合中獲取gradeName和sectionName的_id並存儲在第三個集合中說mergeddetails
合並詳情:
[{"grade_id":"60f819e04a9d43158cabad55","section_id":"60f819e04a9d43158cabad54","maximumStudents":12},{"grade_id":"60f819e04a9d43158cabad59","section_id":"60f819e04a9d43158cabad5b","maximumStudents":13}]
其中grade_id是對應gradeName的_id,section_id是對應sectionName的_id請幫助mongodb quire我正在使用nodejs編寫API
您需要對這兩個集合使用$lookup
db.student.aggregate([
{ $lookup:
{ from: "grade",
localField: "gradeName",
foreignField: "grade",
as: "grade"
}
},
{$lookup:
{ from: "section",
localField: "sectionName",
foreignField: "section",
as: "section"
}
},
{ $unwind: "$grade" },
{ $unwind: "$section" },
{$project:
{
_id:0,
"grade_id":"$grade._id",
"section_id":"$section._id",
maxStudent:1
}
}
])
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