OrientDB-按日期分组查询

Question

I'm trying to execute a query in OrientDB to get the number of posts per day. However, my GROUP BY query is failing, and I fail to see what I'm doing wrong.

I have a database filled with 3 Posts, all with a different date.

This is my query:

select
    datePosted.format("dd-MM-yyyy") as day, count(*)
from
    Post
group by
    day

However, it doesn't work. I would expect it to retrieve a structure with the number of posts per day, but it just retrieves only one result:

[#-2:1{count:3} v0]

Any suggestions?

Answer 1

I created this structure and I think that's similar to yours:

create class Post

create property Post.datePosted date

insert into Post (datePosted) values ('2016-01-25')
insert into Post (datePosted) values ('2016-01-28')
insert into Post (datePosted) values ('2016-01-25')
insert into Post (datePosted) values ('2016-02-04')

These are my options to retrieve the results you want:

First query :

select day, count(*) as posts from (select datePosted.format('yyyy-MM-dd') as day from Post) 
group by day

Output :

----+------+----------+-----
#   |@CLASS|day       |posts
----+------+----------+-----
0   |null  |2016-01-25|2
1   |null  |2016-01-28|1
2   |null  |2016-02-04|1
----+------+----------+-----

Second query :

select datePosted.format('yyyy-MM-dd'), count(*) as posts from Post group by datePosted

Output :

----+------+----------+-----
#   |@CLASS|datePosted|posts
----+------+----------+-----
0   |null  |2016-01-25|2
1   |null  |2016-01-28|1
2   |null  |2016-02-04|1
----+------+----------+-----

Hope it helps

EDITED

Here's an example in Java:

Java Code :

private static String remote = "remote:localhost/";
    public static void main(String[] args) {
        String dbName = "DBname";
        String path = remote + dbName;
        OServerAdmin serverAdmin;
        try {
            serverAdmin = new OServerAdmin(path).connect("root", "root");
            if (serverAdmin.existsDatabase()) { // if DB already exists
                System.out.println("Database '" + dbName + "' already exists");
                ODatabaseDocumentTx db = new ODatabaseDocumentTx(path);
                db.open("root", "root");
                Iterable<ODocument> results = db
                    .command(new OSQLSynchQuery<ODocument>(
                            "select day, count(*) as posts from (select datePosted.format('yyyy-MM-dd') as day from Post) group by day"))
                    .execute();
                for (ODocument result : results) {
                    System.out.println("Day: " + result.field("day") + "   Posts: " + result.field("posts"));
                }
                db.close();
            }
            else {
                serverAdmin.createDatabase(dbName, "document", "plocal");
                System.out.println("Database " + dbName + " created");
            }
            serverAdmin.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

Output :

Day: 2016-01-25   Posts: 2
Day: 2016-01-28   Posts: 1
Day: 2016-02-04   Posts: 1