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I would like to retrieve a list of values that comes from the oldest document currently signed.But i failed to select a document absed on the date.Thanks
here is json :
"ad" : "noc3",
"createdDate" : ISODate(),
"list" : [
{
"id" : "p45",
"value" : 21,
},
{
"id" : "p6",
"value" : 20,
},
{
"id" : "4578",
"value" : 319
}
]
and here my aggregate request :
db.friends.aggregate({$match:{advertiser:"noc3", {$sort:{timestamps:-1},{$limit:1} }},{$unwind:"$list"},{$project:{_id: "$list.id", value:{$add:[0]}}});
793
In MongoDb, the aggregation is assisted by several methods and operators that can perform different tasks. Among those operators, the $sort operator helps to sort the documents and return the documents in an organized order. And for group sorting in MongoDB, the $group operator is used with the $sort operator.
To sort the whole array by value, or to sort by array elements that are not documents, identify the input array and specify 1 for an ascending sort or -1 for descending sort in the sortBy parameter.
If you have documents that store dates as Date objects, but you want to return them in a different format, you can use the $dateToString aggregate pipeline operator. The $dateToString operator converts the Date object to a string, and optionally allows you to specify a format for the resulting output.
Ascending/Descending SortSpecify in the sort parameter the field or fields to sort by and a value of 1 or -1 to specify an ascending or descending sort respectively. When comparing values of different BSON types, MongoDB uses the following comparison order, from lowest to highest: MinKey (internal type) Null.
Your aggregate query is incorrect. You add the sort and limit to the match, but that's now how you do that. You use different pipeline operators:
db.friends.aggregate( [
{ $match: { advertiser: "noc3" } },
{ $sort: { createdDate: -1 } },
{ $limit: 1 },
Your other pipeline operators are bit strange too, and your code vs query mismatches on timestamps vs createdDate. If you add the expected output, I can update the answer to include the last bits of the query too.
188
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