Objectbox-java: Hope to have something like sql GROUP BY or SELECT DISTINCT

[AndroidJohnsonWang]

Hope to have something like sql GROUP BY or SELECT DISTINCT，thanks.

[greenrobot]

Can you give some examples for your use cases? E.g. would you like to select a single value or multiple ones?

[AndroidJohnsonWang]

@greenrobot
For example, I need to query songs by the singer or album classification database, or I need to classify APP users according to a different value, but the query value is uncertain

[DJafari]

@greenrobot this is an example :

for this sample data :

| id | title | date |
|-- | ---- | --- |
| 1 | item1 | 2017/10/01 |
| 2 | item2 | 2017/10/02 |
| 3 | item3 | 2017/10/04 |
| 4 | item2 | 2017/10/06 |
| 5 | item4 | 2017/10/07 |
| 6 | item1 | 2017/10/08 |

if we want DISTINCT title, result data must be :

| id | title | date |
|-- | ---- | --- |
| 1 | item1 | 2017/10/01 |
| 2 | item2 | 2017/10/02 |
| 3 | item3 | 2017/10/04 |
| 5 | item4 | 2017/10/07 |

[greenrobot]

@DJafari Would you be interested in only the title property, or would you want to have full objects as a result?

[DJafari]

@greenrobot i updated my sample, because in objectbox can not possible to select fields, sure it must return full object but unique depends on distinct field

[ajans]

I have a need for something like GROUP BY, too, as I want to deduplicate a list of clicked offers by their external offer-id's (every offer can be clicked multiple times and every click has to be recorded).

I think to accomodate most needs, something like DISTINCT could be implemented like this:

String[] Query.distinctStrings(Property property);
long[] Query.distinctLongs(Property property);
float[] Query.distinctFloats(Property property);
double[] Query.distinctDoubles(Property property);

Whereas something like GROUP BY could be implemented like this:

QueryBuilder<T> QueryBuilder.groupBy(Property property);

Of course, the question would be, how the groups would be represented within the resulting collection (maybe something like List<List<T>>?), or if the groups would simply be flattened e.g. to their first item to keep the result as a List<T>.

[vishnupriyaanil]

Hi @DJafari did you found the solution for your question

[greenrobot]

I'm in line with @ajans suggestions.
Would something like String[] Query.distinctStrings(Property property); (and a variante for int, long, ...) do the trick for most of you?

[aliaksei135]

Seems to have gone a bit quiet here, but I am still looking for this kind of functionality and what @ajans and @greenrobot have described above would be great!

[sandsaber]

+1 here

[greenrobot]

This is deployed via version 1.4.0-RC - please check it out.
Usage: Call the new Query.property method to get a PropertyQuery object. Here, you can config via methods distinct() and unique() before you call one of the find... methods to get primitive results.

[greenrobot]

1.4.0 is here: http://objectbox.io/objectbox-1-4-property-queries-entity-inheritance/

[gauravgajjar]

Hi @greenrobot , @DJafari & @vishnupriyaanil did you find any solution to get object using distinct()

[mecoFarid]

@greenrobot Wouldn't that be more helpful if we got the objects instead of the property?