$year (aggregation)¶

Definition定义¶

$year¶

Returns the year portion of a date.返回日期的年份部分。

The $year expression has the following operator expression syntax:$year表达式具有以下运算符表达式语法：

{ $year: <dateExpression> }

Changed in version 3.6.在版本3.6中更改。

The argument must be a valid expression that resolves to one of the following:参数必须是解析为以下之一的有效表达式：

• A Date, a Timestamp, or an ObjectID.
• A document of the following form:以下形式的文件：

  New in version 3.6.版本3.6中的新功能。

  { date: <dateExpression>, timezone: <tzExpression> }

  Field字段	Description描述
  date	The date to which the operator is applied. <dateExpression> must be a valid expression that resolves to a Date, a Timestamp, or an ObjectID.
  timezone	Optional. The timezone of the operation result. <tzExpression> must be a valid expression that resolves to a string formatted as either an Olson Timezone Identifier or a UTC Offset. If no timezone is provided, the result is displayed in UTC. Format Examples Olson Timezone Identifier "America/New_York" "Europe/London" "GMT" UTC Offset +/-[hh]:[mm], e.g. "+04:45" +/-[hh][mm], e.g. "-0530" +/-[hh], e.g. "+03"

Behavior行为¶

{ $year: new Date("2016-01-01") }

{ $year: { date: new Date("Jan 7, 2003") } }

{ $year: {
    date: new Date("August 14, 2011"),
    timezone: "America/Chicago"
} }

{ $year: ISODate("1998-11-07T00:00:00Z") }

{ $year: {
    date: ISODate("1998-11-07T00:00:00Z"),
    timezone: "-0400"
} }

{ $year: "March 28, 1976" }

{ $year: Date("2016-01-01") }

{ $year: "2009-04-09" }

Example示例¶

Consider a sales collection with the following documents:考虑一个sales集合带有以下文档：

{
  "_id" : 1,
  "item" : "abc",
  "price" : 10,
  "quantity" : 2,
  "date" : ISODate("2014-01-01T08:15:39.736Z")
}

The following aggregation uses the $year and other date operators to break down the date field:以下聚合使用$year和其他日期运算符来分解日期字段：

db.sales.aggregate(
   [
     {
       $project:
         {
year: { $year: "$date" },           month: { $month: "$date" },
           day: { $dayOfMonth: "$date" },
           hour: { $hour: "$date" },
           minutes: { $minute: "$date" },
           seconds: { $second: "$date" },
           milliseconds: { $millisecond: "$date" },
           dayOfYear: { $dayOfYear: "$date" },
           dayOfWeek: { $dayOfWeek: "$date" },
           week: { $week: "$date" }
         }
     }
   ]
)

The operation returns the following result:操作返回以下结果：

{
  "_id" : 1,
  "year" : 2014,
  "month" : 1,
  "day" : 1,
  "hour" : 8,
  "minutes" : 15,
  "seconds" : 39,
  "milliseconds" : 736,
  "dayOfYear" : 1,
  "dayOfWeek" : 4,
  "week" : 0
}