MongoDB Update Operator
The following modifiers are available to update operations. For example – in db.collection.update() and db.collection.findAndModify().
Defines the operator expression in the document of the form:
Field Operator
$currentDate
It updates the elements of a field to the current date, either as a Date or a timestamp. The default data type of this operator is the date.
Syntax:
Example:
$inc
It increases a filed by the specified value.
Syntax:
Example:
$min
It changes the value of the field to a specified value if the specified value is less than the current value of the filed.
Syntax:
Example:
$max
It changes the value of the field to a specified value if the specified value is greater than the current value of the filed.
Syntax:
Example:
$mul
It multiplies the value of a field by a number.
Syntax:
Example:
$rename
The rename operator changes the name of a field.
Syntax:
Example:
$set
The set operator changes the value of a field with the specified value.
Syntax:
Example:
$setOnInsert
If the upsert is set to true, then it results in an insert of a document, then setOnInsert operator assigns the specified values to the field in the document.
Syntax:
$unset
It removes a specified field.
Syntax:
Example:
Array Operators
$
We can update an element in an array without explicitly specifying the position of the element.
Syntax:
Example:
$[ ]
The positional operator indicates that the update operator should change all the elements in the given array field.
Syntax:
Example:
$[<identifier>]
It is called a filtered positional operator that identifies the array elements.
Syntax:
Example:
$addToSet
It adds an element to an array unless the element is already present, in which case this operator does nothing to that array.
Syntax:
Example:
$pop
We can remove the first or last element of an array using the pop operator. We need to pass the value of pop as -1 to remove the first element of an array and 1 to remove the last element in an array.
Syntax:
Example:
$pull
Using a pull operator, we can remove all the instances of a value in an array that matches the specified condition.
Syntax:
Example:
$push
It appends a specified value to an array.
Syntax:
Example:
$pullAll
We can remove all instances of the specified value from an existing array using the pullAll operator. It removes elements that match the listed value.
Syntax:
Example:
Modifiers
$each
It is used with the $addToSet operator and the $push operator. It is used with the addToSet operator to add multiple values to an array if the value does not exist in the field.
Syntax:
It is used with the push operator to append multiple values to an array.
Syntax:
Example:
$position
It specifies the location where the push operator inserts elements inside an array.
Syntax:
Example:
$slice
This modifier is used to limit the number of array elements during the push operation.
Syntax:
Example:
$sort
The sort modifier arranges the values of an array during the push operation.
Syntax:
Example:
Bitwise Operator
$bit
The bit operator updates a field using a bitwise operation. It supports bitwise AND, bitwise OR, and bitwise XOR operations.
Syntax:
Example: