在一个MongoDB文档中获取两个数组中的唯一值
让我们创建一个包含文档的集合-
>db.demo608.insertOne({"ListOfName1":["John","Chris","Bob","David"],"ListOfName2":["Bob", "Sam","John","Robert","Chris"]}
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5e974542f57d0dc0b182d62b")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo608.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5e974542f57d0dc0b182d62b"),
"ListOfName1" : [
"John",
"Chris",
"Bob",
"David"
],
"ListOfName2" : [
"Bob",
"Sam",
"John",
"Robert",
"Chris"
]
}以下是查询以在一个MongoDB文档中的两个数组中获取唯一值-
> db.demo608.aggregate([
... {$project:{SetOfNames:{$setUnion:['$ListOfName1','$ListOfName2']}}}
... ]).pretty();这将产生以下输出-
{
"_id" : ObjectId("5e974542f57d0dc0b182d62b"),
"SetOfNames" : [
"Bob",
"Chris",
"David",
"John",
"Robert",
"Sam"
]
}