Push array to array mongodb

Docs HomeMongoDB Manual

$push
Push array to array mongodb

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

The $push operator has the form:

{ $push: { <field1>: <value1>, ... } }

To specify a <field> 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: { <field1>: { <modifier1>: <value1>, ... }, ... } }

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

  1. Update array to add elements in the correct position.

  2. Apply sort, if specified.

  3. Slice the array, if specified.

  4. 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 $[<identifier>] 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: { <field1>: <value|condition>, <field2>: <value|condition>, ... } } To specify a <field> in an embedded document or in an array, use dot notation.

Tải thêm tài liệu liên quan đến bài viết Push array to array mongodb