用 MongoDB 查询收集唯一的数组项目
> db.demo588.insertOne({"CountryName":["US","AUS","UK","US","UK","AUS"]});{
"acknowledged" : true, "insertedId" : ObjectId("5e92bbd2fd2d90c177b5bccb")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo588.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5e92bbd2fd2d90c177b5bccb"),
"CountryName" : [
"US",
"AUS",
"UK",
"US",
"UK",
"AUS"
]
}以下是收集唯一数组项的查询-
> db.demo588.distinct("CountryName");这将产生以下输出-
[ "AUS", "UK", "US" ]