如何查询MongoDB集合？
要查询或返回MongoDB集合，请使用getCollection()。让我们创建一个包含文档的集合-
> db.demo294.insertOne({"EmployeeId":101,"EmployeeName":"Chris"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e4d4a1a5d93261e4bc9ea36")
}
> db.demo294.insertOne({"EmployeeId":102,"EmployeeName":"Bob"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e4d4a255d93261e4bc9ea37")
}
> db.demo294.insertOne({"EmployeeId":103,"EmployeeName":"David"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e4d4a335d93261e4bc9ea38")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo294.find();
这将产生以下输出-
{ "_id" : ObjectId("5e4d4a1a5d93261e4bc9ea36"), "EmployeeId" : 101, "EmployeeName" : "Chris" }
{ "_id" : ObjectId("5e4d4a255d93261e4bc9ea37"), "EmployeeId" : 102, "EmployeeName" : "Bob" }
{ "_id" : ObjectId("5e4d4a335d93261e4bc9ea38"), "EmployeeId" : 103, "EmployeeName" : "David" }以下是获取MongoDB集合的查询-
> db.getCollection('demo294').find({
... "EmployeeId":{$in:[101,103]}});这将产生以下输出-
{ "_id" : ObjectId("5e4d4a1a5d93261e4bc9ea36"), "EmployeeId" : 101, "EmployeeName" : "Chris" }
{ "_id" : ObjectId("5e4d4a335d93261e4bc9ea38"), "EmployeeId" : 103, "EmployeeName" : "David" }