获取MongoDB中的最大值和最小值？
将$max和$min运算符与聚合框架一起使用以获取最大值和最小值。首先让我们创建一个包含文档的集合-
> db.maxAndMinDemo.insertOne({"Value":98});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd698a357806ebf1256f129")
}
> db.maxAndMinDemo.insertOne({"Value":97});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd698af57806ebf1256f12a")
}
> db.maxAndMinDemo.insertOne({"Value":69});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd698b357806ebf1256f12b")
}
> db.maxAndMinDemo.insertOne({"Value":96});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd698b657806ebf1256f12c")
}
> db.maxAndMinDemo.insertOne({"Value":99});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd698b957806ebf1256f12d")
}以下是在find()方法的帮助下显示集合中所有文档的查询-
> db.maxAndMinDemo.find().pretty();
这将产生以下输出-
{ "_id" : ObjectId("5cd698a357806ebf1256f129"), "Value" : 98 }
{ "_id" : ObjectId("5cd698af57806ebf1256f12a"), "Value" : 97 }
{ "_id" : ObjectId("5cd698b357806ebf1256f12b"), "Value" : 69 }
{ "_id" : ObjectId("5cd698b657806ebf1256f12c"), "Value" : 96 }
{ "_id" : ObjectId("5cd698b957806ebf1256f12d"), "Value" : 99 }以下是对MongoDB中的max和min的查询-
> db.maxAndMinDemo.aggregate([
{ "$group": {
"_id": null,
"MaximumValue": { "$max": "$Value" },
"MinimumValue": { "$min": "$Value" }
}}
]);这将产生以下输出-
{ "_id" : null, "MaximumValue" : 99, "MinimumValue" : 69 }