Database
db={"books":[{"_id":"SHN-E3AE0DB3BC7D-4214-BDAE-59140DA1F850","nameOfBook":"test","nameOfAuthor":"test authou","yearOfPublication":"1998","publication":"test","edition":"test","status":"available","price":"test"}],"bookStocks":[{"_id":"SHNC-E1C6CF22A055-4A7E-AB79-CAEDC65AB29C","bookId":"SHN-E3AE0DB3BC7D-4214-BDAE-59140DA1F850","collegeId":"COL-D0E03FA4803F-4224-A321-1801626A9942","course":"bcom","bookDetails":"eeff","status":"available"}]}
Query
db.books.aggregate([{$lookup:{from:"bookStocks",let:{bookId:"$_id"},pipeline:[{$match:{$and:[{$expr:{$eq:["$$bookId","$bookId"]}},{"collegeId":"COL-D0E03FA4803F-4224-A321-1801626A9942"}]}}],as:"bookStocks"}},{$match:{bookStocks:{$ne:[]}}}])