如何计算MongoDB文档中的键数？
没有内置功能来计算文档中的键数。为了计算键的数量，您需要编写一些代码。
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.numberofKeysInADocumentDemo.insertOne({
"UserName":"John","UserAge":21,"UserEmailId":"john12@gmail.com","UserCountryName":"US"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c9132584afe5c1d2279d6ac")
}在find()method的帮助下显示集合中的所有文档。查询如下-
> db.numberofKeysInADocumentDemo.find().pretty();
以下是输出-
{
"_id" : ObjectId("5c9132584afe5c1d2279d6ac"),
"UserName" : "John",
"UserAge" : 21,
"UserEmailId" : "john12@gmail.com",
"UserCountryName" : "US"
}这是查询文档中的键数的查询-
> myDocument = db.numberofKeysInADocumentDemo.findOne({});
{
"_id" : ObjectId("5c9132584afe5c1d2279d6ac"),
"UserName" : "John",
"UserAge" : 21,
"UserEmailId" : "john12@gmail.com",
"UserCountryName" : "US"
}
> numberOfKeys=0;
0
> for(i in myDocument){numberOfKeys ++;}
4
> print("The document has "+ "" +numberOfKeys +" Keys");以下是输出-
The document has 5 Keys