在MongoDB中如何获取游标值
要在MongoDB中获取游标的值，请使用hasNext()。让我们创建一个包含文档的集合-
> db.demo191.insertOne({"EmployeeId":1,"EmployeeName":"Chris Brown"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3ad95303d395bdc21346c5")
}
> db.demo191.insertOne({"EmployeeId":2,"EmployeeName":"David Miller"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3ad95f03d395bdc21346c6")
}
> db.demo191.insertOne({"EmployeeId":1,"EmployeeName":"John Doe"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3ad96803d395bdc21346c7")
}
> db.demo191.insertOne({"EmployeeId":1,"EmployeeName":"John Smith"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3ad97003d395bdc21346c8")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo191.find();
这将产生以下输出-
{ "_id" : ObjectId("5e3ad95303d395bdc21346c5"), "EmployeeId" : 1, "EmployeeName" : "Chris Brown" }
{ "_id" : ObjectId("5e3ad95f03d395bdc21346c6"), "EmployeeId" : 2, "EmployeeName" : "David Miller" }
{ "_id" : ObjectId("5e3ad96803d395bdc21346c7"), "EmployeeId" : 1, "EmployeeName" : "John Doe" }
{ "_id" : ObjectId("5e3ad97003d395bdc21346c8"), "EmployeeId" : 1, "EmployeeName" : "John Smith" }以下是获取光标对象的值的查询-
> var cursor = db.demo191.find( { "EmployeeId":1 } );
> while (cursor.hasNext()) {
... print(tojson(cursor.next()));
...}这将产生以下输出-
{
"_id" : ObjectId("5e3ad95303d395bdc21346c5"),
"EmployeeId" : 1,
"EmployeeName" : "Chris Brown"
}
{
"_id" : ObjectId("5e3ad96803d395bdc21346c7"),
"EmployeeId" : 1,
"EmployeeName" : "John Doe"
}
{
"_id" : ObjectId("5e3ad97003d395bdc21346c8"),
"EmployeeId" : 1,
"EmployeeName" : "John Smith"
}