MongoDB：$ nin和$ in不能在$ elemMatch中一起工作以获取主题为“ MongoDB”而不是“ Java”的文档
对于此类获取，仅使用$nin和$in。让我们创建一个包含文档的集合-
> db.demo140.insertOne({"Id":101,"Subjects":["MongoDB","MySQL"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e31c149fdf09dd6d08539a9")
}
> db.demo140.insertOne({"Id":102,"Subjects":["MongoDB","Java"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e31c14cfdf09dd6d08539aa")
}
> db.demo140.insertOne({"Id":103,"Subjects":["MongoDB","PL/SQL"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e31c157fdf09dd6d08539ab")
}
> db.demo140.insertOne({"Id":104,"Subjects":["MongoDB","SQL Server"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e31c163fdf09dd6d08539ac")
}
> db.demo140.insertOne({"Id":105,"Subjects":["C","C++"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e31c16ffdf09dd6d08539ad")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo140.find();
这将产生以下输出-
{ "_id" : ObjectId("5e31c149fdf09dd6d08539a9"), "Id" : 101, "Subjects" : [ "MongoDB", "MySQL" ] }
{ "_id" : ObjectId("5e31c14cfdf09dd6d08539aa"), "Id" : 102, "Subjects" : [ "MongoDB", "Java" ] }
{ "_id" : ObjectId("5e31c157fdf09dd6d08539ab"), "Id" : 103, "Subjects" : [ "MongoDB", "PL/SQL" ] }
{ "_id" : ObjectId("5e31c163fdf09dd6d08539ac"), "Id" : 104, "Subjects" : [ "MongoDB", "SQL Server" ] }
{ "_id" : ObjectId("5e31c16ffdf09dd6d08539ad"), "Id" : 105, "Subjects" : [ "C", "C++" ] }这是获取主题为“MongoDB”但主题为“Java”的文档的查询-
> db.demo140.find({$and:[{Subjects:{$in:['MongoDB']}}, {Subjects:{$nin:['Java']}}]}).toArray();这将产生以下输出-
[
{
"_id" : ObjectId("5e31c149fdf09dd6d08539a9"),
"Id" : 101,
"Subjects" : [
"MongoDB",
"MySQL"
]
},
{
"_id" : ObjectId("5e31c157fdf09dd6d08539ab"),
"Id" : 103,
"Subjects" : [
"MongoDB",
"PL/SQL"
]
},
{
"_id" : ObjectId("5e31c163fdf09dd6d08539ac"),
"Id" : 104,
"Subjects" : [
"MongoDB",
"SQL Server"
]
}
]