$lookup in mongodb
{
$lookup:
{
from: <collection to join>,
localField: <field from the input documents>,
foreignField: <field from the documents of the "from" collection>,
as: <output array field>
}
}$lookup in mongodb
{
$lookup:
{
from: <collection to join>,
localField: <field from the input documents>,
foreignField: <field from the documents of the "from" collection>,
as: <output array field>
}
}mongodb aggregate lookup array of objects
db.getCollection('widgets').aggregate([
{ $unwind: '$info' },
{
$lookup: {
from: 'icons',
localField: 'info.iconId',
foreignField: '_id',
as: 'info.icon'
}
},
{ $unwind: '$info.icon' },
{
$group: {
_id: '$_id',
root: { $mergeObjects: '$$ROOT' },
info: { $push: '$info' }
}
},
{
$replaceRoot: {
newRoot: {
$mergeObjects: ['$root', '$$ROOT']
}
}
},
{
$project: {
root: 0
}
}
]);lookup in mongodb
SELECT *, <output array field>FROM collectionWHERE <output array field> IN ( SELECT <documents as determined from the pipeline> FROM <collection to join> WHERE <pipeline>);Copyright © 2021 Codeinu
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