获取跨索引数组字段的不同聚合
mongodbbig data analyticsdatabase更新于 2026/1/16 18:07:17
为了获取跨索引数组字段的不同聚合，我们举个例子，创建一个包含一些文档的集合。
以下是创建包含文档的集合的查询
> db.distinctAggregation.insertOne({"UserName":"Larry","UserPost":["Hi","Hello"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c98aefb330fd0aa0d2fe4c6")
}
> db.distinctAggregation.insertOne({"UserName":"Chris","UserPost":["Hi","Good Morning"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c98af0a330fd0aa0d2fe4c7")
}
> db.distinctAggregation.insertOne({"UserName":"Robert","UserPost":["Awesome"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c98af1e330fd0aa0d2fe4c8")
}
以下是借助 find() 方法显示集合中的所有文档的查询
> db.distinctAggregation.find().pretty();
这将产生以下输出 −
{
"_id" : ObjectId("5c98aefb330fd0aa0d2fe4c6"),
"UserName" : "Larry",
"UserPost" : [
"Hi",
"Hello"
]
}
{
"_id" : ObjectId("5c98af0a330fd0aa0d2fe4c7"),
"UserName" : "Chris",
"UserPost" : [
"Hi",
"Good Morning"
]
}
{
"_id" : ObjectId("5c98af1e330fd0aa0d2fe4c8"),
"UserName" : "Robert",
"UserPost" : [
"Awesome"
]
}
以下是在数组字段上创建索引的查询
> db.distinctAggregation.ensureIndex({"UserPost":1});
{
"createdCollectionAutomatically" : false,
"numIndexesBefore" : 1,
"numIndexesAfter" : 2,
"ok" : 1
}
以下是在索引之间获取数组字段唯一聚合的查询
> db.distinctAggregation.distinct("UserPost");
这将产生以下输出 −
[ "Awesome", "Good Morning", "Hello", "Hi" ]
