由于MongoDB而导致的特定领域？

要在MongoDB中获得特定字段的结果，可以使用findOne()。以下是语法-

db.yourCollectionName.findOne({"yourFieldName1":yourValue},{yourFieldName2:1});

首先让我们创建一个包含文档的集合-

> db.particularFieldDemo.insertOne({"EmployeeName":"John Smith","EmployeeAge":26,"EmployeeTechnology":"MongoDB"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5cd9b4abb50a6c6dd317ada2")
}
> db.particularFieldDemo.insertOne({"EmployeeName":"Chris Brown","EmployeeAge":28,"EmployeeTechnology":"Java"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5cd9b4d2b50a6c6dd317ada3")
}
> db.particularFieldDemo.insertOne({"EmployeeName":"David Miller","EmployeeAge":30,"EmployeeTechnology":"MySQL"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5cd9b4e8b50a6c6dd317ada4")
}
> db.particularFieldDemo.insertOne({"EmployeeName":"John Doe","EmployeeAge":31,"EmployeeTechnology":"C++"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5cd9b527b50a6c6dd317ada5")
}

以下是在find()方法的帮助下显示集合中所有文档的查询-

> db.particularFieldDemo.find().pretty();

这将产生以下输出-

{
   "_id" : ObjectId("5cd9b4abb50a6c6dd317ada2"),
   "EmployeeName" : "John Smith",
   "EmployeeAge" : 26,
   "EmployeeTechnology" : "MongoDB"
}
{
   "_id" : ObjectId("5cd9b4d2b50a6c6dd317ada3"),
   "EmployeeName" : "Chris Brown",
   "EmployeeAge" : 28,
   "EmployeeTechnology" : "Java"
}
{
   "_id" : ObjectId("5cd9b4e8b50a6c6dd317ada4"),
   "EmployeeName" : "David Miller",
   "EmployeeAge" : 30,
   "EmployeeTechnology" : "MySQL"
}
{
   "_id" : ObjectId("5cd9b527b50a6c6dd317ada5"),
   "EmployeeName" : "John Doe",
   "EmployeeAge" : 31,
   "EmployeeTechnology" : "C++"
}

以下是在MongoDB中查找特定字段作为结果的查询-

> db.particularFieldDemo.findOne({"EmployeeTechnology":"Java"},{EmployeeName:1});

这将产生以下输出-

{
   "_id" : ObjectId("5cd9b4d2b50a6c6dd317ada3"),
   "EmployeeName" : "Chris Brown"
}