我想执行$lookup，其中localField是ObjectId的字符串表示形式，而外部字段是实际的ObjectId。如果items是字符串值但_id是ObjectId，MongoDB3.2是否可行？[{"$lookup":{"from":"videos","localField":"items","foreignField":"_id","as":"appendedItems"}}] 最佳答案 mongodb3.2版本的$lookup中无法匹配String与ObjectId，有一些ticketsopenedforthisissu

我有两个系列:学生{_id:ObjectId("657..."),name:'abc'},{_id:ObjectId("593..."),name:'xyz'}图书馆{_id:ObjectId("987..."),book_name:'book1',issued_to:[{student:ObjectId("657...")},{student:ObjectId("658...")}]},{_id:ObjectId("898..."),book_name:'book2',issued_to:[{student:ObjectId("593...")},{student:ObjectId(