您可以使用use命令从一个数据库切换到另一个数据库。在这里,我们使用“测试”数据库中的集合。让我们将该集合插入名为“ sample”的另一个数据库中。
为了进一步理解,让我们使用文档创建一个集合。使用文档创建集合的查询如下-
> db.insertOneRecordDemo.insertOne({"UserName":"Larry","UserAge":23}); { "acknowledged" : true, "insertedId" : ObjectId("5c9534de16f542d757e2b452") } > db.insertOneRecordDemo.insertOne({"UserName":"Chris","UserAge":26}); { "acknowledged" : true, "insertedId" : ObjectId("5c9534e816f542d757e2b453") } > db.insertOneRecordDemo.insertOne({"UserName":"David","UserAge":25}); { "acknowledged" : true, "insertedId" : ObjectId("5c9534f116f542d757e2b454") }
在find()
method的帮助下显示集合中的所有文档。查询如下-
> db.insertOneRecordDemo.find().pretty();
以下是输出-
{ "_id" : ObjectId("5c9534de16f542d757e2b452"), "UserName" : "Larry", "UserAge" : 23 } { "_id" : ObjectId("5c9534e816f542d757e2b453"), "UserName" : "Chris", "UserAge" : 26 } { "_id" : ObjectId("5c9534f116f542d757e2b454"), "UserName" : "David", "UserAge" : 25 }
这是将记录从一个MongoDB数据库插入另一个数据库的查询-
> var AllDocumentsFromSourceCollection = db.insertOneRecordDemo.find(); > use sample; switched to db sample > AllDocumentsFromSourceCollection.forEach(function(allRecords){ db.getAllRecordsFromSourceCollectionDemo.insert(allRecords) });
检查记录是否已插入。查询如下-
> db.getAllRecordsFromSourceCollectionDemo.find().pretty();
以下是输出-
{ "_id" : ObjectId("5c9534de16f542d757e2b452"), "UserName" : "Larry", "UserAge" : 23 } { "_id" : ObjectId("5c9534e816f542d757e2b453"), "UserName" : "Chris", "UserAge" : 26 } { "_id" : ObjectId("5c9534f116f542d757e2b454"), "UserName" : "David", "UserAge" : 25 }
现在,您可以检查样本数据库中是否存在集合名称。查询如下-
> show collections;
以下是输出-
arraySizeErrorDemo basicInformationDemo copyThisCollectionToSampleDatabaseDemo deleteAllRecordsDemo deleteDocuments deleteDocumentsDemo deleteSomeInformation documentWithAParticularFieldValueDemo employee findListOfIdsDemo findSubstring getAllRecordsFromSourceCollectionDemo getElementWithMaxIdDemo internalArraySizeDemo largestDocumentDemo makingStudentInformationClone oppositeAddToSetDemo prettyDemo returnOnlyUniqueValuesDemo selectWhereInDemo sourceCollection studentInformation sumOfValueDemo truncateDemo updateInformation userInformation