MongoDB-如何查看字段的所有元素是否包含在超集中？
对于MongoDB中字段的所有元素，请使用，find()并在其中使用$elemMatch。的$elemMatch操作者匹配包含与匹配的所有指定的查询标准中的至少一个元素的数组字段的文档。
让我们创建一个包含文档的集合-
> db.demo624.insertOne({"ListOfName":["John","Chris","David","Bob"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e9ab3ff6c954c74be91e6a5")
}
> db.demo624.insertOne({"ListOfName":["John","Chris"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e9ab4026c954c74be91e6a6")
}
> db.demo624.insertOne({"ListOfName":["John","Chris","Carol"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e9ab4076c954c74be91e6a7")
}
> db.demo624.insertOne({"ListOfName":["John","Chris","Bob"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e9ab40e6c954c74be91e6a8")
}
> db.demo624.insertOne({"ListOfName":["John","Chris","Mike","Robert"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e9ab4186c954c74be91e6a9")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo624.find();
这将产生以下输出-
{ "_id" : ObjectId("5e9ab3ff6c954c74be91e6a5"), "ListOfName" : [ "John", "Chris", "David", "Bob" ] }
{ "_id" : ObjectId("5e9ab4026c954c74be91e6a6"), "ListOfName" : [ "John", "Chris" ] }
{ "_id" : ObjectId("5e9ab4076c954c74be91e6a7"), "ListOfName" : [ "John", "Chris", "Carol" ] }
{ "_id" : ObjectId("5e9ab40e6c954c74be91e6a8"), "ListOfName" : [ "John", "Chris", "Bob" ] }
{ "_id" : ObjectId("5e9ab4186c954c74be91e6a9"), "ListOfName" : [ "John", "Chris", "Mike", "Robert" ] }以下是查询以查看字段的所有元素是否包含在超集中-
> db.demo624.find({"ListOfName":{$not:{$elemMatch:{$nin:["John", "Chris", "David", "Bob"]}}}});这将产生以下输出-
{ "_id" : ObjectId("5e9ab3ff6c954c74be91e6a5"), "ListOfName" : [ "John", "Chris", "David", "Bob" ] }
{ "_id" : ObjectId("5e9ab4026c954c74be91e6a6"), "ListOfName" : [ "John", "Chris" ] }
{ "_id" : ObjectId("5e9ab40e6c954c74be91e6a8"), "ListOfName" : [ "John", "Chris", "Bob" ] }