$zip (array expression)
APPLIES TO: MongoDB vCore
The $zip
operator is used to merge two or more arrays element-wise into a single array of arrays. It is useful when you want to combine related elements from multiple arrays into a single array structure.
Syntax
The syntax for the $zip
operator is as follows:
{
$zip: {
inputs: [ <array1>, <array2>, ... ],
useLongestLength: <boolean>, // Optional
defaults: <array> // Optional
}
}
Parameters
Description | |
---|---|
inputs |
An array of arrays to be merged element-wise. |
useLongestLength |
A boolean value that, if set to true, uses the longest length of the input arrays. If false or not specified, it uses the shortest length. |
defaults |
An array of default values to use if useLongestLength is true and any input array is shorter than the longest array. |
Example
Let's understand the usage with sample json from stores
dataset.
{
"_id": "988d2dd1-2faa-4072-b420-b91b95cbfd60",
"name": "Lakeshore Retail",
"location": {
"lat": -51.3041,
"lon": -166.0838
},
"staff": {
"totalStaff": {
"fullTime": 5,
"partTime": 20
}
},
"sales": {
"totalSales": 266491,
"salesByCategory": [
{
"categoryName": "Towel Racks",
"totalSales": 13237
},
{
"categoryName": "Washcloths",
"totalSales": 44315
},
{
"categoryName": "Face Towels",
"totalSales": 42095
},
{
"categoryName": "Toothbrush Holders",
"totalSales": 47912
},
{
"categoryName": "Hybrid Mattresses",
"totalSales": 48660
},
{
"categoryName": "Napkins"
},
{
"categoryName": "Pillow Cases",
"totalSales": 38833
}
]
}
}
Example 1: Basic Usage
Suppose you want to merge the categoryName
and totalSales
fields from the salesByCategory
array.
db.stores.aggregate([
{ $match: {"_id": "988d2dd1-2faa-4072-b420-b91b95cbfd60"} },
{
$project: {
name:1,
categoryNames: "$sales.salesByCategory.categoryName",
totalSales: "$sales.salesByCategory.totalSales",
categoryWithSales: {
$zip: {
inputs: ["$sales.salesByCategory.categoryName", "$sales.salesByCategory.totalSales"],
useLongestLength: false
}
}
}
}
])
This will produce an output for individual array of arrays under categoryWithSales
field. useLongestLength
set to true
would return the following output, while a value of false
will remove the Napkins
array from the output.
{
"_id": "988d2dd1-2faa-4072-b420-b91b95cbfd60",
"name": "Lakeshore Retail",
"categoryNames": [
"Towel Racks",
"Washcloths",
"Face Towels",
"Toothbrush Holders",
"Hybrid Mattresses",
"Napkins",
"Pillow Cases"
],
"totalSales": [
13237, 44315,
42095, 47912,
48660, 38833
],
"categoryWithSales": [
["Towel Racks", 13237],
["Washcloths", 44315],
["Face Towels", 42095],
["Toothbrush Holders", 47912],
["Hybrid Mattresses", 48660],
["Napkins", null],
["Pillow Cases", 38833]
]
}
Related content
- Review options for Migrating from MongoDB to Azure Cosmos DB for MongoDB (vCore)
- Read more about Feature compatibility with MongoDB