使用MongoDB在数组项上实现$ dateToString
要在数组项上实现$dateToString，请aggregate()在MongoDB中使用。让我们创建一个包含文档的集合-
> db.demo104.insertOne(
... {
...
... "AppName" : "Online Book",
... "Details" : [
... {
... "ClientName" : "Chris",
... "Deadline" : new ISODate("2020-03-10")
... }
... ]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5e2ed7fd9fd5fd66da21446f")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo104.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5e2ed7fd9fd5fd66da21446f"),
"AppName" : "Online Book",
"Details" : [
{
"ClientName" : "Chris",
"Deadline" : ISODate("2020-03-10T00:00:00Z")
}
]
}以下是对数组项实现$dateToString的查询-
> db.demo104.aggregate([
... { "$match": {}},
... { "$project": {
... "title": 1,
... "Details": {
... "$map": {
... "input": "$Details",
... "as": "out",
... "in": {
... "ClientName": "$$out.ClientName",
... "Deadline": {
... "$dateToString": { "format": "%m", "date": "$$out.Deadline" }
... }
... }
... }
... }
... }}
... ])这将产生以下输出-
{ "_id" : ObjectId("5e2ed7fd9fd5fd66da21446f"), "Details" : [ { "ClientName" : "Chris", "Deadline" : "03" } ] }