在MongoDB查询中创建别名？
您可以使用聚合框架创建别名。首先让我们创建一个包含文档的集合-
> db.creatingAliasDemo.insertOne({_id:101,"Name":"John Doe"});
{ "acknowledged" : true, "insertedId" : 101 }
> db.creatingAliasDemo.insertOne({_id:102,"Name":"David Miller"});
{ "acknowledged" : true, "insertedId" : 102 }
> db.creatingAliasDemo.insertOne({_id:103,"Name":"Sam Williams"});
{ "acknowledged" : true, "insertedId" : 103 }以下是在find()方法的帮助下显示集合中所有文档的查询-
> db.creatingAliasDemo.find().pretty();
这将产生以下输出-
{ "_id" : 101, "Name" : "John Doe" }
{ "_id" : 102, "Name" : "David Miller" }
{ "_id" : 103, "Name" : "Sam Williams" }以下是在查询中创建别名的查询-
> db.creatingAliasDemo.aggregate(
... [
... {
... $project: {
... _id:1,
... "FullName":"$Name"
... }
... }
... ]
... );这将产生以下输出-
{ "_id" : 101, "FullName" : "John Doe" }
{ "_id" : 102, "FullName" : "David Miller" }
{ "_id" : 103, "FullName" : "Sam Williams" }