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Nagarajan R
Nagarajan R

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Answer: MongoDB nested lookup with 3 levels

The cause of your 'troubles' is the second aggregation stage - { $unwind: "$address" }. It removes record for party with _id: 4 (because its address array is empty, as you mention) and produces two records for parties _id: 1 and _id: 5 (because each of them has two…

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Dimer Bwimba • Edited