MongoDB查询以查找每个文档中三个键的最早日期
要查找最早的日期，请在MongoDB中使用$minaggregate()。让我们创建一个包含文档的集合-
> db.demo353.insertOne({"Date1":new ISODate("2019-01-10"),"Date2":new ISODate("2016-01-21"),"Date3":new ISODate("2020-04-11")});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e568261f8647eb59e5620be")
}
> db.demo353.insertOne({"Date1":new ISODate("2011-11-20"),"Date2":new ISODate("2013-12-10"),"Date3":new ISODate("2014-01-05")});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e56827ff8647eb59e5620bf")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo353.find();
这将产生以下输出-
{ "_id" : ObjectId("5e568261f8647eb59e5620be"), "Date1" : ISODate("2019-01-10T00:00:00Z"), "Date2" : ISODate("2016-01-21T00:00:00Z"), "Date3" : ISODate("2020-04-11T00:00:00Z") }
{ "_id" : ObjectId("5e56827ff8647eb59e5620bf"), "Date1" : ISODate("2011-11-20T00:00:00Z"), "Date2" : ISODate("2013-12-10T00:00:00Z"), "Date3" : ISODate("2014-01-05T00:00:00Z") }以下是查询以查找每个文档中最早的日期-
> db.demo353.aggregate([
... {
... $project: {
... OldestDate: {
... $min: [
... { $ifNull: [ "$Date1", new Date() ] },
... { $ifNull: [ "$Date2", new Date() ] },
... { $ifNull: [ "$Date3", new Date() ] },
... ]
... }
... }
... }
... ])这将产生以下输出-
{ "_id" : ObjectId("5e568261f8647eb59e5620be"), "OldestDate" : ISODate("2016-01-21T00:00:00Z") }
{ "_id" : ObjectId("5e56827ff8647eb59e5620bf"), "OldestDate" : ISODate("2011-11-20T00:00:00Z") }