如何从MongoDB文档中的双嵌套数组中删除元素？
要从MongoDB文档中的双嵌套数组中删除元素，可以使用$pull运算符。
为了理解这个概念，让我们用文档创建一个集合。使用文档创建集合的查询如下-
> db.removeElementFromDoublyNestedArrayDemo.insertOne(
... {
... "_id" : "1",
... "UserName" : "Larry",
... "UserDetails" : [
... {
... "UserCountryName" : "US",
... "UserLocation" : [
... {
... "UserCityName" : "New York"
... },
... {
... "UserZipCode" : "10001"
... }
... ]
... }
... ]
... }
... );
{ "acknowledged" : true, "insertedId" : "1" }
> db.removeElementFromDoublyNestedArrayDemo.insertOne(
... {
... "_id" : "2",
... "UserName" : "Mike",
... "UserDetails" : [
... {
... "UserCountryName" : "UK",
... "UserLocation" : [
... {
... "UserCityName" : "Bangor"
... },
... {
... "UserZipCode" : "20010"
... }
... ]
... }
... ]
... }
... );
{ "acknowledged" : true, "insertedId" : "2" }在find()method的帮助下显示集合中的所有文档。查询如下-
> db.removeElementFromDoublyNestedArrayDemo.find().pretty();
以下是输出-
{
"_id" : "1",
"UserName" : "Larry",
"UserDetails" : [
{
"UserCountryName" : "US",
"UserLocation" : [
{
"UserCityName" : "New York"
},
{
"UserZipCode" : "10001"
}
]
}
]
}
{
"_id" : "2",
"UserName" : "Mike",
"UserDetails" : [
{
"UserCountryName" : "UK",
"UserLocation" : [
{
"UserCityName" : "Bangor"
},
{
"UserZipCode" : "20010"
}
]
}
]
}这是从MongoDB文档中的双嵌套数组中删除元素的查询-
> db.removeElementFromDoublyNestedArrayDemo.update(
... { _id : "2" },
... {$pull : {"UserDetails.0.UserLocation" : {"UserZipCode":"20010"}}}
... );
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })让我们借助来检查集合中的文档find()。查询如下-
> db.removeElementFromDoublyNestedArrayDemo.find().pretty();
以下是输出-
{
"_id" : "1",
"UserName" : "Larry",
"UserDetails" : [
{
"UserCountryName" : "US",
"UserLocation" : [
{
"UserCityName" : "New York"
},
{
"UserZipCode" : "10001"
}
]
}
]
}
{
"_id" : "2",
"UserName" : "Mike",
"UserDetails" : [
{
"UserCountryName" : "UK",
"UserLocation" : [
{
"UserCityName" : "Bangor"
}
]
}
]
}现在，字段“UserZipCode”：“20010”已从双重嵌套数组中删除。