Concatenate String

Combine string variables to use in Aggregation Pipeline

Situation: You have a “first name” and “last name” you want to concatenate to use in a $project stage.

Note: We filter for males only, then also limit results to 10 documents.

# match by gender first if want to filter for only male
db.contacts.aggregate([
    {$match: {gender: "male"}},
    {$project: {_id: 0, name: {$concat: ["$name.first", " ", "$name.last"]}, birthdate: {$toDate: "$dob.date"}}},
    {$sort: {birthdate: 1}},
    {$skip: 10},
    {$limit: 10}
]).pretty()

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