calculate SUM for single column with DbFlow

Question

I'm using latest version of DBFLOW library and i'm trying to calculate sum single column as countOfNewPosts

this is my table:

public class CafeWebNewPostInformation extends BaseModel {
    @PrimaryKey
    @Column
    public int id;

    @Column
    public int cafeWebServerId;

    @Column
    public int countOfNewPosts;

    @Column
    @ForeignKey(tableClass = AlachiqCafeWebs.class,
            references = @ForeignKeyReference(columnName = "parentId", foreignKeyColumnName = "id"))
    private int parentId;

    @Column
    public int lastSavedId;

    @Column
    public int lastRequestedId;

    @Column
    public int lastRetrievedId;
}

and this is my code to get that from this table:

CafeWebNewPostInformation countOfNewPost =
        SQLite.select(
                Method.sum(CafeWebNewPostInformation_Table.countOfNewPosts).as("count")
        )
                .from(CafeWebNewPostInformation.class).querySingle();

i dont get any error and this is result of that:

ScreenShot:

what happen and where is count on this result?

score 4 · Accepted Answer · answered Aug 03 '17 at 08:50

problem solved

think about it. you are calling

SELECT SUM(`countOfNewPosts`) as 'count' FROM `CafeWebNewPostInformation`

Meaning the results you get back only contain a single row of count from that query. You wont get any error since we don't implement strict column matching on a Cursor. You need to define a @QueryModel QueryModels that has a single field called count:

@QueryModel // (add database reference)
public class CountOfPost {

  @Column
  public int count;
}

then

CountOfPost count = SQLite.select(
  Method.sum(CafeWebNewPostInformation_Table.countOfNewPosts).as("count"))
  .from(CafeWebNewPostInformation.class)
  .queryCustomSingle(CountOfPost.class);

or you can instead of calling querySingle() call count().

reference

calculate SUM for single column with DbFlow

1 Answers1