$dateTrunc (operador de expressão )

binSize e unit campos

Together, binSize and unit specify the time period used in the $dateTrunc calculation.

Por exemplo:

• If binSize is 1 and unit is hour, the time period is one hour. For the date 2021-03-20T11:30:05Z, $dateTrunc returns 2021-03-20T11:00:00Z.

• If binSize is 2 and unit is hour, the time period is two hours. For the date 2021-03-20T11:30:05Z, $dateTrunc returns 2021-03-20T10:00:00Z.

$dateTrunc:

• Divides the time for the $dateTrunc calculation into binSize time periods in the specified time unit.

  The time periods start at a reference date, which is determined by unit. If unit is:

  • A string other than week, $dateTrunc uses a reference date of 2000-01-01T00:00:00.00Z. For example, if binSize is 10 and unit is year, example time periods are:

    • 2000-01-01T00:00:00.00Z

    • 2010-01-01T00:00:00.00Z

    • 2020-01-01T00:00:00.00Z

  • Equal to week, $dateTrunc uses a reference date that is set to the earliest first day of the week that is greater than or equal to 2000-01-01. The first day is set using startOfWeek (the default is Sunday).

• Returns the lower boundary of the time period that the date is in. The boundary is returned as an ISODate. If the binSize field is 1, $dateTrunc sets the least significant parts (as determined by unit) of the returned ISODate to 0 and keeps the rest of the ISODate the same.

Se a unidade for:

• year: $dateTrunc returns the ISODate for the start of January 1 for the year in date.

• quarter: $dateTrunc returns the ISODate for the start of the first day of the calendar quarter in date.

  Os trimestres são:

  • De janeiro a março

  • De abril a junho

  • De julho a setembro

  • De outubro a dezembro

• month: $dateTrunc returns the ISODate for the start of the first day of the month in date.

• week: $dateTrunc returns the ISODate for the start of the startOfWeek day in date. The default for startOfWeek is Sunday.

• day: $dateTrunc returns the ISODate for the start of the day in date.

• hour: $dateTrunc returns the ISODate for the start of the hour in date.

• minute: $dateTrunc returns the ISODate for the start of the minute in date.

• second: $dateTrunc returns the ISODate for start of the second in date.

unit e startOfWeek campos

Se a unidade for:

• Uma string diferente de week, startOfWeek é ignorada.

• Igual a week e startOfWeek é:

  • Specified: $dateTrunc uses startOfWeek as the first day of the week for the calculation.

  • Omitted: $dateTrunc uses Sunday as the start of the week for the calculation.

Truncar datas de pedido em um estágio de pipeline $project

This example uses $dateTrunc in a $project stage to truncate the cake sales orderDate values to two weeks:

db.cakeSales.aggregate( [
   {
      $project: {
         _id: 1,
         orderDate: 1,
         truncatedOrderDate: {
            $dateTrunc: {
               date: "$orderDate", unit: "week", binSize: 2,
               timezone: "America/Los_Angeles", startOfWeek: "Monday"
            }
         }
      }
   }
] )

No exemplo:

• $project inclui os campos _id, orderDate e truncatedOrderDate na saída.

• $dateTrunc truncates the orderDate field to a 2 binSize week unit time period in the America/Los_Angeles timezone with startOfWeek set to Monday.

Neste exemplo de saída, o orderDate truncado é mostrado no campo truncatedOrderDate:

[
   {
      _id: 0,
      orderDate: ISODate("2020-05-18T14:10:30.000Z"),
      truncatedOrderDate: ISODate("2020-05-11T07:00:00.000Z")
   },
   {
      _id: 1,
      orderDate: ISODate("2021-03-20T11:30:05.000Z"),
      truncatedOrderDate: ISODate("2021-03-15T07:00:00.000Z")
   },
   {
      _id: 2,
      orderDate: ISODate("2021-01-11T06:31:15.000Z"),
      truncatedOrderDate: ISODate("2021-01-04T08:00:00.000Z")
   },
   {
      _id: 3,
      orderDate: ISODate("2020-02-08T13:13:23.000Z"),
      truncatedOrderDate: ISODate("2020-02-03T08:00:00.000Z")
   },
   {
      _id: 4,
      orderDate: ISODate("2019-05-18T16:09:01.000Z"),
      truncatedOrderDate: ISODate("2019-05-13T07:00:00.000Z")
   },
   {
      _id: 5,
      orderDate: ISODate("2019-01-08T06:12:03.000Z"),
      truncatedOrderDate: ISODate("2019-01-07T08:00:00.000Z")
   }
]

Truncar datas de pedidos e obter soma de quantidade em um $group estágio de pipeline

Este exemplo usa $dateTrunc em um estágio $group para truncar os valores orderDate de vendas do bolo para seis meses e retornar a soma dos valores quantity:

db.cakeSales.aggregate( [
   {
      $group: {
         _id: {
            truncatedOrderDate: {
               $dateTrunc: {
                  date: "$orderDate", unit: "month", binSize: 6
               }
            }
         },
         sumQuantity: { $sum: "$quantity" }
      }
   }
] )

No exemplo:

• $group tem o campo _id configurado para o campo truncatedOrderDate para agrupar os documentos cakeSales e retorna a soma dos valores quantity para cada grupo utilizando $sum.

• $dateTrunc truncates the orderDate field to a 6 binSize month unit time period.

Neste exemplo de saída, o orderDate truncado é mostrado no campo truncatedOrderDate e a soma quantity é mostrada no campo sumQuantity :

[
   {
      _id: { truncatedOrderDate: ISODate("2020-01-01T00:00:00.000Z") },
      sumQuantity: 224
   },
   {
      _id: { truncatedOrderDate: ISODate("2021-01-01T00:00:00.000Z") },
      sumQuantity: 285
   },
   {
      _id: { truncatedOrderDate: ISODate("2019-01-01T00:00:00.000Z") },
      sumQuantity: 296
   }
]