MongoDB Group通过设置状态
为此，您可以aggregate()在MongoDB中使用。让我们创建一个包含文档的集合-
> db.demo149.insertOne({"Status":40});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e350386fdf09dd6d08539c4")
}
> db.demo149.insertOne({"Status":40});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e350388fdf09dd6d08539c5")
}
> db.demo149.insertOne({"Status":50});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e35038afdf09dd6d08539c6")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo149.find();
这将产生以下输出-
{ "_id" : ObjectId("5e350386fdf09dd6d08539c4"), "Status" : 40 }
{ "_id" : ObjectId("5e350388fdf09dd6d08539c5"), "Status" : 40 }
{ "_id" : ObjectId("5e35038afdf09dd6d08539c6"), "Status" : 50 }这是对MongoDB组的查询-
> db.demo149.aggregate([
... {
... "$group": {
... "_id": null,
... "done": {
... "$push": {
... "$cond": [
... { "$eq": [ "$Status", 40 ] },
... { "_id": "$_id", "Status": "$Status" },
... false
... ]
... }
... },
... "notdone": {
... "$push": {
... "$cond": [
... { "$eq": [ "$Status", 50 ] },
... { "_id": "$_id", "Status": "$Status" },
... false
... ]
... }
... }
... }
... },
... {
... "$project": {
... "_id": 0,
... "done": {
... "$setDifference": [ "$done", [false] ]
... },
... "notdone": {
... "$setDifference": [ "$notdone", [false] ]
... }
... }
... }
... ]);这将产生以下输出-
{
"done" : [
{ "_id" : ObjectId("5e350386fdf09dd6d08539c4"), "Status" : 40 },
{ "_id" : ObjectId("5e350388fdf09dd6d08539c5"), "Status" : 40 } ], "notdone" : [
{ "_id" : ObjectId("5e35038afdf09dd6d08539c6"), "Status" : 50 }
]
}