在这种情况下,请在特定字段上使用索引的概念。首先让我们创建一个包含文档的集合。在这里,我们还使用createIndex()
-创建了索引
> db.decreasetimeusingindex.createIndex({"StudentName":1}); { "createdCollectionAutomatically" : true, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 } > db.decreasetimeusingindex.insertOne({"StudentName":"John Smith","StudentAge":21}); { "acknowledged" : true, "insertedId" : ObjectId("5e03960af5e889d7a51994ff") } > db.decreasetimeusingindex.insertOne({"StudentName":"John Doe","StudentAge":24}); { "acknowledged" : true, "insertedId" : ObjectId("5e039611f5e889d7a5199500") } > db.decreasetimeusingindex.insertOne({"StudentName":"Adam Smith","StudentAge":22}); { "acknowledged" : true, "insertedId" : ObjectId("5e03961df5e889d7a5199501") }
以下是在find()
方法的帮助下显示集合中所有文档的查询-
> db.decreasetimeusingindex.find().pretty();
这将产生以下输出-
{ "_id" : ObjectId("5e03960af5e889d7a51994ff"), "StudentName" : "John Smith", "StudentAge" : 21 } { "_id" : ObjectId("5e039611f5e889d7a5199500"), "StudentName" : "John Doe", "StudentAge" : 24 } { "_id" : ObjectId("5e03961df5e889d7a5199501"), "StudentName" : "Adam Smith", "StudentAge" : 22 }
以下是查找特定记录的查询-
> db.decreasetimeusingindex.find({"StudentName":"Adam Smith"});
这将产生以下输出-
{ "_id" : ObjectId("5e03961df5e889d7a5199501"), "StudentName" : "Adam Smith", "StudentAge" : 22 }