How to create dummy values in a collection in MongoDB

[joe nisha]

I dont know how to create dummy values in collections in MongoDB. In other words I want to know the mongo query that is equivalent the SQL query below

select id, "hello" as constval, 1 as no from sample;

Can someone please help me on this. 

[Jeff Lee]

If your goal is to seed a collection with data you can do something like this:

> for (var i=1;i <= 10; i++){ db.foo.save({ _id:i, thename:Array(10).join('a') })}

> db.foo.find()

{ "_id" : 1, "thename" : "aaaaaaaaa" }

{ "_id" : 2, "thename" : "aaaaaaaaa" }

{ "_id" : 3, "thename" : "aaaaaaaaa" }

{ "_id" : 4, "thename" : "aaaaaaaaa" }

{ "_id" : 5, "thename" : "aaaaaaaaa" }

{ "_id" : 6, "thename" : "aaaaaaaaa" }

{ "_id" : 7, "thename" : "aaaaaaaaa" }

{ "_id" : 8, "thename" : "aaaaaaaaa" }

{ "_id" : 9, "thename" : "aaaaaaaaa" }

{ "_id" : 10, "thename" : "aaaaaaaaa" }

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[joe nisha]

Thanks for the reply. I dont want to add values or make modification to the collection, just want the values from the select query for internal processing as in the query

select id, "aaa" as num from test; 

through this query only the value appears in the query result but the table does not get modified. Is there anything equivalent in mongodb?

[Jeff Lee]

The only ways that I'm aware of is to either use a bit of javascript to append to the document:

e.g.

> db.foods.find()

{ "_id" : ObjectId("5228a2750a59bf1df4bf4b7e"), "name" : "apple" }

> db.foods.find().forEach(function(x){x.type = 'fruit'; printjson(x);})

{

        "_id" : ObjectId("5228a2750a59bf1df4bf4b7e"),

        "name" : "apple",

        "type" : "fruit"

}

or with aggregation:

> db.foods.aggregate({$project:{_id:1, name:1, type:{$concat:'fruit'}}})

{

        "result" : [

                {

                        "_id" : ObjectId("5228a2750a59bf1df4bf4b7e"),

                        "name" : "apple",

                        "type" : "fruit"

                }

        ],

        "ok" : 1

}

There may be something easier.