Database Management Systems
In MongoDB, the $dayOfWeek aggregation pipeline operator returns the day of the week for a date as a number between 1 (Sunday) and 7 (Saturday).
You can optionally specify a timezone to use for the result.
The $dayOfWeek operator accepts either a date (as either a Date, a Timestamp, or an ObjectId), or a document that specifies the date and timezone to use.
In MongoDB, the $dayOfMonth aggregation pipeline operator returns the day of the month for a date as a number between 1 and 31.
You can optionally specify a timezone to use for the result.
The $dayOfMonth operator accepts either a date (as either a Date, a Timestamp, or an ObjectId), or a document that specifies the date and timezone to use.
In MongoDB, the $dayOfYear aggregation pipeline operator returns the day of the year for a date as a number between 1 and 366.
You can optionally specify a timezone to use for the result.
The $dayOfYear operator accepts either a date (as either a Date, a Timestamp, or an ObjectId), or a document that specifies the date and timezone to use.
In MongoDB, when you update documents that contain arrays, you have the option of using the arrayFilters parameter.
The arrayFilters parameter allows you to specify an array of filter documents that determine which array elements to modify.
In the update document, use the $[<identifier>] filtered positional operator, which identifies the array elements that match the arrayFilters conditions for the update operation.
In MongoDB, you can use the $unset field update operator to completely remove a field from a document.
The $unset operator is designed specifically to delete a field and its value from the document.
In MongoDB, the $currentDate operator sets the value of a field to the current date.
It can be set as either a Date or a timestamp type. The default is Date.
$currentDate is an update operator, and can only be used when updating documents, not when inserting them (although it can be used in upsert operations).
In MongoDB, the $toDate aggregation operator converts a value to a date
$toDate takes any valid expression. If the expression can’t be converted to a date, it returns an error. If the expression is null or missing, it returns null.
The MongoDB $set update operator replaces the value of a field with the specified value.
It’s used in conjunction with update operations, for example when using the update() method to update a document.
MongoDB has a $mul field update operator that allows you to multiply a value by a specific amount.
If the field doesn’t already exist, it is created and its value is set to zero (0) using the same numeric type as the multiplier.
MongoDB has an $inc field update operator that allows you to increment a value by a specific amount.
You can use positive and negative values (i.e. to increment or decrement the value).
If the field doesn’t already exist, it is created with the specified value.
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