Push array to array mongodb

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$push

The $push operator appends a specified value to an array.

The $push operator has the form:

{ $push: { : , ... } }

To specify a in an embedded document or in an array, use dot notation.

Starting in MongoDB 5.0, update operators process document fields with string-based names in lexicographic order. Fields with numeric names are processed in numeric order. See Update Operators Behavior for details.

If the field is absent in the document to update, $push adds the array field with the value as its element.

If the field is not an array, the operation will fail.

If the value is an array, $push appends the whole array as a single element. To add each element of the value separately, use the $each modifier with $push. For an example, see Append a Value to Arrays in Multiple Documents. For a list of modifiers available for $push, see Modifiers.

Starting in MongoDB 5.0, mongod no longer raises an error when you use an update operator like $push with an empty operand expression [ { } ]. An empty update results in no changes and no oplog entry is created [meaning that the operation is a no-op].

You can use the $push operator with the following modifiers:

Modifier

Description

`$each`	Appends multiple values to the array field.
`$slice`	Limits the number of array elements. Requires the use of the `$each` modifier.
`$sort`	Orders elements of the array. Requires the use of the `$each` modifier.
`$position`	Specifies the location in the array at which to insert the new elements. Requires the use of the `$each` modifier. Without the `$position` modifier, the `$push` appends the elements to the end of the array.

When used with modifiers, the $push operator has the form:

{ $push: { : { : , ... }, ... } }

The processing of the $push operation with modifiers occur in the following order, regardless of the order in which the modifiers appear:

Update array to add elements in the correct position.
Apply sort, if specified.
Slice the array, if specified.
Store the array.

Create the students collection:

db.students.insertOne[ { _id: 1, scores: [ 44, 78, 38, 80 ] } ]

The following example appends 89 to the scores array:

db.students.updateOne[
   { _id: 1 },
   { $push: { scores: 89 } }
]

Example output:

{ _id: 1, scores: [ 44, 78, 38, 80, 89 ] }

Add the following documents to the students collection:

db.students.insertMany[ [
   { _id: 2, scores: [ 45, 78, 38, 80, 89 ] } ,
   { _id: 3, scores: [ 46, 78, 38, 80, 89 ] } ,
   { _id: 4, scores: [ 47, 78, 38, 80, 89 ] }
] ]

The following $push operation appends 95 to the scores array in each document:

db.students.updateMany[
   { },
   { $push: { scores: 95 } }
]

To confirm that each scores array includes 95, run the following operation:

The operation returns the following results:

[
   { _id: 1, scores: [ 44, 78, 38, 80, 89, 95 ] },
   { _id: 2, scores: [ 45, 78, 38, 80, 89, 95 ] },
   { _id: 3, scores: [ 46, 78, 38, 80, 89, 95 ] },
   { _id: 4, scores: [ 47, 78, 38, 80, 89, 95 ] }
]

Use $push with the $each modifier to append multiple values to the array field.

The following example appends each element of [ 90, 92, 85 ] to the scores array for the document where the name field equals joe:

db.students.updateOne[
   { name: "joe" },
   { $push: { scores: { $each: [ 90, 92, 85 ] } } }
]

Add the following document to the students collection:

db.students.insertOne[
   {
      "_id" : 5,
      "quizzes" : [
         { "wk": 1, "score" : 10 },
         { "wk": 2, "score" : 8 },
         { "wk": 3, "score" : 5 },
         { "wk": 4, "score" : 6 }
      ]
   }
]

The following $push operation uses:

the $each modifier to add multiple documents to the quizzes array,
the $sort modifier to sort all the elements of the modified quizzes array by the score field in descending order, and
the $slice modifier to keep only the first three sorted elements of the quizzes array.

db.students.updateOne[
   { _id: 5 },
   {
     $push: {
       quizzes: {
          $each: [ { wk: 5, score: 8 }, { wk: 6, score: 7 }, { wk: 7, score: 6 } ],
          $sort: { score: -1 },
          $slice: 3
       }
     }
   }
]

After the operation only the three highest scoring quizzes are in the array:

{
  "_id" : 5,
  "quizzes" : [
     { "wk" : 1, "score" : 10 },
     { "wk" : 2, "score" : 8 },
     { "wk" : 5, "score" : 8 }
  ]
}

Tip

How do I update an array in MongoDB?

You can use the updateOne[] or updateMany[] methods to add, update, or remove array elements based on the specified criteria. It is recommended to use the updateMany[] method to update multiple arrays in a collection.

How do I update a nested array in MongoDB?

Update Nested Arrays in Conjunction with $[] The $[] filtered positional operator, in conjunction with the $[] all positional operator, can be used to update nested arrays. The following updates the values that are greater than or equal to 8 in the nested grades.

What is $Set in MongoDB?

$set outputs documents that contain all existing fields from the input documents and newly added fields. The $set stage is an alias for $addFields . Both stages are equivalent to a $project stage that explicitly specifies all existing fields in the input documents and adds the new fields.

What is $pull in MongoDB?

The $pull operator removes from an existing array all instances of a value or values that match a specified condition. The $pull operator has the form: { $pull: { : , : , ... } } To specify a in an embedded document or in an array, use dot notation.

Tip

How do I update an array in MongoDB?

How do I update a nested array in MongoDB?

What is $Set in MongoDB?

What is $pull in MongoDB?

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