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"
}