QSqlRelationalTableModel - relation with multiple columns

[Tupla]

Hi everybody.
I know there is already a post related to this topic ("this one":http://qt-project.org/forums/viewthread/7744), but I don't seem to get this work.
Problem:
I have one database table containing a list of people, and another table that has a foreign key to the id of the person. If I wanted to display first name and last name of a person in a table view or while using a mapper, given that first name and last name are in different columns, how could I do this using QSqlRelationalTableModel?

Link suggested to subclass QAbstractProxyModel, I tried to subclass QSortFilterProxyModel and reimplement the data() function setting the "person" model as source model, but in this way mapper does not work: data are displayed inside the combobox (initially empty), but navigating through the records the value inside the combobox does not change...
Moreover, I don't understand what should be the source model of my proxy model: should it be the relational model, or the table model "pointed to" by the relation?
Some hints on how to proceed would be greatly appreciated :)

[Tupla]

Does anybody know the solution?

[franku]

Keep trying with the QSqlRelationalTableModel. Have you read the "documentation":http://doc.qt.digia.com/qt/qsqlrelationaltablemodel.html? There you can find an example on how to make multiple relations.

[Tupla]

Yes, I read the code snippet related to the creation of multiple relationships, but that's not what I'm trying to achieve.
I would like to have something like this:

Table 1: employee
ID_E | First_name | Last_name | Other

Table 2: project
ID_P | Employee

Setting a QSqlRelationalTableModel on the table "project", and a relationship between the column "Employee" and the ID in the table employee, I would like to have displayed in that column both the first and last names. I see that QSqlRelationalTableModel only allows to set one column for display purpose for each relationship. I would like to display the values of two columns without having to insert an additional column in the database and setting another relationship.
I hope my problem is clearer in this way.

Thank you for your reply.

[franku]

1. I am no sql expert, but can't you use a SQLView in the database itself for this request (instead of SELECT * from project WHERE...)?

2. On the other hand you could use just the QSqlTableModel and reimplement the ::data() and ::columnCount() to fake the extra column for the Project's QTableView.

[Tupla]

[quote author="franku" date="1351891016"]1. I am no sql expert, but can't you use a SQLView in the database itself for this request (instead of SELECT * from project WHERE...)?[/quote]
Do you mean creating a view which concatenates the first and last name and use that as "table" to QSqlTableModel?
[quote author="franku" date="1351891016"]
2. On the other hand you could use just the QSqlTableModel and reimplement the ::data() and ::columnCount() to fake the extra column for the Project's QTableView.[/quote]
That would be an option, I thought about reimplementing those function in QSqlRelationalTableModel to include also the "last_name" column when displaying data for the foreign key reference, but I would prefer a cleaner approach using a proxy model, if there exists one.

In the link I posted in the first post (which is more or less the same problem I have), there seems to be a solution using a subclass of QAbstractProxyModel, the only thing is that I can't figure it out.

[QtTester]

I have the same problem, can anyone to solve this?
for example:
table1:

id  shotname longname

table2:

id list table1Id 

in the QSqlRelationalTableModel example , we can have these fields result:

id list shotname

// or this
id list longname

but how can we display more column like this?:

id list shotname longname

here is my test and work, but CANNOT be editable:

    QSqlQuery query(db);
    QSqlQueryModel *m = new QSqlQueryModel(this);
    query.exec("SELECT table2.id, table2.list, table1.shotname, table1.longname FROM table2"
               "INNER JOIN table1 ON table2.table1Id= table1.id");
    m->setQuery(query);

    ui->tableView->setModel(m);

[JonB]

@QtTester
The title of this thread was

QSqlRelationalTableModel - relation with multiple columns

Your solution, and the ones mentioned above, do not relate to a QSqlRelationalTableModel. That can have multiple QSqlRelations if desired. I do not know whether that allows the same column to be mapped twice to two different columns in one foreign table, but you could try it, I can't see why it would not be allowed. Ah, no, I see, it can have multiple setRelation(column, QSqlRelation())s, but each column specified can only have one relation, not multiple ones in a list, it seems.

Your SELECT statement is fine, but yes of course what you get from that is a non-editable model.