db={"linkedDetails":[{_id:"1234avshjd",book_id:"16262ahahha",author_id:"127hjajaj"},{_id:"223ahha78",book_id:"1681awtsy",author_id:"127hjajaj"},{_id:"97ahj238",book_id:"126ashs17",author_id:"127hjajaj"},{_id:"138hajq12",book_id:"12742ahjsn",author_id:"4728haja72"}],"bookDetails":[{_id:"16262ahahha",book_name:"harry potter",book_price:10},{_id:"1681awtsy",book_name:"lotr",book_price:10},{_id:"12742ahjsn",book_name:"song of sea",book_price:10}]}

db.linkedDetails.aggregate({"$match":{author_id:"4728haja72"}},{"$lookup":{"from":"bookDetails","localField":"book_id","foreignField":"_id",as:"books"}})