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$isoDayOfWeek

Returns the weekday number in ISO 8601 format, ranging from 1 (Monday) to 7 (Sunday). The operator accepts a date expression that resolves to a Date, Timestamp, or ObjectId.

Syntax

$isoDayOfWeek: <dateExpression>

Parameters

dateExpressionobjectrequired

An expression that resolves to a Date, Timestamp, or ObjectId. If the expression resolves to null or is missing, $isoDayOfWeek returns null.

Examples

Analyze promotion events by day of week

This query reviews promotion events to see which days of the week they started on.

Query:

db.stores.aggregate([
  { $match: {"_id": "40d6f4d7-50cd-4929-9a07-0a7a133c2e74"} },
  { $unwind: "$promotionEvents" },
  {
    $project: {
      eventName: "$promotionEvents.eventName",
      startDate: {
        $dateFromParts: {
          year: "$promotionEvents.promotionalDates.startDate.Year",
          month: "$promotionEvents.promotionalDates.startDate.Month",
          day: "$promotionEvents.promotionalDates.startDate.Day"
        }
      }
    }
  },
  {
    $group: {
      _id: { $isoDayOfWeek: "$startDate" },
      eventCount: { $sum: 1 },
      events: { $push: "$eventName" }
    }
  },
  {
    $project: {
      _id: 1,
      dayName: {
        $switch: {
          branches: [
            { case: { $eq: ["$_id", 1] }, then: "Monday" },
            { case: { $eq: ["$_id", 2] }, then: "Tuesday" },
            { case: { $eq: ["$_id", 3] }, then: "Wednesday" },
            { case: { $eq: ["$_id", 4] }, then: "Thursday" },
            { case: { $eq: ["$_id", 5] }, then: "Friday" },
            { case: { $eq: ["$_id", 6] }, then: "Saturday" },
            { case: { $eq: ["$_id", 7] }, then: "Sunday" }
          ]
        }
      },
      eventCount: 1,
      events: 1
    }
  },
  { $sort: { "_id": 1 } }
])

Output:

[
  {
    "_id": 1,
    "eventCount": 1,
    "events": ["Super Sale Spectacular"],
    "dayName": "Monday"
  },
  {
    "_id": 2,
    "eventCount": 1,
    "events": ["Discount Delight Days"],
    "dayName": "Tuesday"
  },
  {
    "_id": 3,
    "eventCount": 1,
    "events": ["Fantastic Deal Days"],
    "dayName": "Wednesday"
  },
  {
    "_id": 4,
    "eventCount": 1,
    "events": ["Massive Markdown Mania"],
    "dayName": "Thursday"
  },
  {
    "_id": 6,
    "eventCount": 1,
    "events": ["Major Bargain Bash"],
    "dayName": "Saturday"
  },
  {
    "_id": 7,
    "eventCount": 1,
    "events": ["Grand Deal Days"],
    "dayName": "Sunday"
  }
]

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