MongoDB查询以从包含一些重复记录的文档中获取最小值和最大值
为此，请使用aggregate()和$group。要获得最小值和最大值，请使用$min和$max。
让我们创建一个包含文档的集合-
> db.demo167.insertOne({"Score":60});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3693a79e4f06af551997d1")
}
> db.demo167.insertOne({"Score":80});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3693ab9e4f06af551997d2")
}
> db.demo167.insertOne({"Score":60});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3693ad9e4f06af551997d3")
}
> db.demo167.insertOne({"Score":90});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3693b09e4f06af551997d4")
}
> db.demo167.insertOne({"Score":89});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3693b69e4f06af551997d5")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo167.find();
这将产生以下输出-
{ "_id" : ObjectId("5e3693a79e4f06af551997d1"), "Score" : 60 }
{ "_id" : ObjectId("5e3693ab9e4f06af551997d2"), "Score" : 80 }
{ "_id" : ObjectId("5e3693ad9e4f06af551997d3"), "Score" : 60 }
{ "_id" : ObjectId("5e3693b09e4f06af551997d4"), "Score" : 90 }
{ "_id" : ObjectId("5e3693b69e4f06af551997d5"), "Score" : 89 }以下是获取最小值和最大值的查询-
> var d = [
... {
... "$group": {
... "_id": "id",
... "MinimumValue": { "$min": "$Score" },
... "MaximumValue": { "$max": "$Score" }
... }
... }
... ]
> db.demo167.aggregate(d);这将产生以下输出-
{ "_id" : "id", "MinimumValue" : 60, "MaximumValue" : 90 }