MongoDB查询以终端命令汇总特定键值？
为此，将$match和一起使用aggregate()。让我们创建一个包含文档的集合-
> db.demo329.insertOne({"Name":"Chris","Age":21,"Marks":45});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e516f28f8647eb59e56207d")
}
> db.demo329.insertOne({"Name":"David","Age":21,"Marks":56});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e516f28f8647eb59e56207e")
}
> db.demo329.insertOne({"Name":"Mike","Age":21,"Marks":78});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e516f29f8647eb59e56207f")
}
> db.demo329.insertOne({"Name":"David","Age":21,"Marks":89});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e516f29f8647eb59e562080")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo329.find().pretty();
这将产生以下输出：
{
"_id" : ObjectId("5e516f28f8647eb59e56207d"),
"Name" : "Chris",
"Age" : 21,
"Marks" : 45
}
{
"_id" : ObjectId("5e516f28f8647eb59e56207e"),
"Name" : "David",
"Age" : 21,
"Marks" : 56
}
{
"_id" : ObjectId("5e516f29f8647eb59e56207f"),
"Name" : "Mike",
"Age" : 21,
"Marks" : 78
}
{
"_id" : ObjectId("5e516f29f8647eb59e562080"),
"Name" : "David",
"Age" : 21,
"Marks" : 89
}以下是对键值求和的查询-
> db.demo329.aggregate([
... {
... $match: {
... $and: [
... { 'Name': 'David'},
... { Age:21}
.. ]
... }
... },
... {
... $group: {
... _id: null,
... TotalMarks: { $sum: "$Marks" }
... }
... }
... ])这将产生以下输出-
{ "_id" : null, "TotalMarks" : 145 }