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- $isoWeekYear (aggregation)
$isoWeekYear (aggregation)¶
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Definition¶
- $isoWeekYear¶
3.4 新版功能.
Returns the year number in ISO 8601 format. The year starts with the Monday of week 1 (ISO 8601) and ends with the Sunday of the last week (ISO 8601).
$isoWeekYear has the following operator expression syntax:
{ $isoWeekYear: <date expression> }
The argument can be any valid expression that resolves to a BSON ISODate object, a BSON Timestamp object, or a Date object.
Behavior¶
| Example | Result |
|---|---|
| { $isoWeekYear: new Date("2016-01-01") } | 2015 |
| { $isoWeekYear: new Date("2015-01-01") } | 2015 |
| { $isoWeekYear: new Date("2016-01-04") } | 2016 |
| { $isoWeekYear: "2016-01-01" } | error |
注解
$isoWeekYear cannot take a string as an argument.
Example¶
A collection called anniversaries contains the following documents:
{ "_id" : 1, "date" : ISODate("2016-01-01T00:00:00Z") }
{ "_id" : 2, "date" : ISODate("2016-01-04T00:00:00Z") }
{ "_id" : 3, "date" : ISODate("2015-01-01T00:00:00Z") }
{ "_id" : 4, "date" : ISODate("2014-04-21T00:00:00Z") }
The following operation returns the year number in ISO 8601 format for each date field.
db.anniversaries.aggregate( [
{
$project: {
yearNumber: { $isoWeekYear: "$date" }
}
}
] )
The operation returns the following results:
{ "_id" : 1, "yearNumber" : 2015 }
{ "_id" : 2, "yearNumber" : 2016 }
{ "_id" : 3, "yearNumber" : 2015 }
{ "_id" : 4, "yearNumber" : 2014 }