value might be applied to the database at once, or it may be    cached in the model.    Returns true if the value could be set, or false on error (for    example, if \a index is out of bounds).    For relational columns, \a value must be the index, not the    display value.    \sa editStrategy(), data(), submit(), revertRow()*/bool QSqlRelationalTableModel::setData(const QModelIndex &index, const QVariant &value,                                       int role){    Q_D(QSqlRelationalTableModel);    if (role == Qt::DisplayRole && index.column() > 0 && index.column() < d->relations.count()) {        d->relations[index.column()].displayValues[index.row()] = value;        return true;    }    return QSqlTableModel::setData(index, value, role);}/*!    Lets the specified \a column be a foreign index specified by \a relation.    Example:    \quotefromfile sql/relationaltablemodel/relationaltablemodel.cpp    \skipto model->setTable    \printline model->setTable    \skipto setRelation    \printline setRelation    The setRelation() call specifies that column 2 in table \c    employee is a foreign key that maps with field \c id of table \c    city, and that the view should present the \c{city}'s \c name    field to the user.    Note: The table's primary key may not contain a relation to another table.    \sa relation()*/void QSqlRelationalTableModel::setRelation(int column, const QSqlRelation &relation){    Q_D(QSqlRelationalTableModel);    if (column < 0)        return;    if (d->relations.size() <= column)        d->relations.resize(column + 1);    d->relations[column].rel = relation;}/*!    Returns the relation for the column \a column, or an invalid    relation if no relation is set.    \sa setRelation(), QSqlRelation::isValid()*/QSqlRelation QSqlRelationalTableModel::relation(int column) const{    Q_D(const QSqlRelationalTableModel);    return d->relations.value(column).rel;}QString QSqlRelationalTableModelPrivate::escapedRelationField(const QString &tableName,                        const QString &fieldName) const{    QString esc;    esc.reserve(tableName.size() + fieldName.size() + 1);    esc.append(tableName).append(QLatin1Char('.')).append(fieldName);    return db.driver()->escapeIdentifier(esc, QSqlDriver::FieldName);}/*!    \reimp*/QString QSqlRelationalTableModel::selectStatement() const{    Q_D(const QSqlRelationalTableModel);    QString query;    if (tableName().isEmpty())        return query;    if (d->relations.isEmpty())        return QSqlTableModel::selectStatement();    QString tList;    QString fList;    QString where;    QSqlRecord rec = d->baseRec;    QStringList tables;    const QRelation nullRelation;    for (int i = 0; i < rec.count(); ++i) {        QSqlRelation relation = d->relations.value(i, nullRelation).rel;        if (relation.isValid()) {            QString relTableAlias = QString::fromLatin1("relTblAl_%1").arg(i);            fList.append(d->escapedRelationField(relTableAlias, relation.displayColumn()));            fList.append(QLatin1Char(','));            if (!tables.contains(relation.tableName()))                tables.append(d->db.driver()->escapeIdentifier(relation.tableName(),                       QSqlDriver::TableName).append(QLatin1String(" AS ")).append(                       d->db.driver()->escapeIdentifier(relTableAlias, QSqlDriver::TableName)));            where.append(d->escapedRelationField(tableName(), rec.fieldName(i)));            where.append(QLatin1Char('='));            where.append(d->escapedRelationField(relTableAlias, relation.indexColumn()));            where.append(QLatin1String(" AND "));        } else {            fList.append(d->escapedRelationField(tableName(), rec.fieldName(i)));            fList.append(QLatin1Char(','));        }    }    if (!tables.isEmpty())        tList.append(tables.join(QLatin1String(","))).append(QLatin1String(","));    if (fList.isEmpty())        return query;    tList.prepend(QLatin1Char(',')).prepend(d->db.driver()->escapeIdentifier(tableName(),                QSqlDriver::TableName));    // truncate tailing comma    tList.chop(1);    fList.chop(1);    query.append(QLatin1String("SELECT "));    query.append(fList).append(QLatin1String(" FROM ")).append(tList);    if (!where.isEmpty())        where.chop(5);    qAppendWhereClause(query, where, filter());    QString orderBy = orderByClause();    if (!orderBy.isEmpty())        query.append(QLatin1Char(' ')).append(orderBy);    return query;}/*!    Returns a QSqlTableModel object for accessing the table for which    \a column is a foreign key, or 0 if there is no relation for the    given \a column.    The returned object is owned by the QSqlRelationalTableModel.    \sa setRelation(), relation()*/QSqlTableModel *QSqlRelationalTableModel::relationModel(int column) const{    Q_D(const QSqlRelationalTableModel);    QRelation relation = d->relations.value(column);    if (!relation.rel.isValid())        return 0;    QSqlTableModel *childModel = relation.model;    if (!childModel) {        childModel = new QSqlTableModel(const_cast<QSqlRelationalTableModel *>(this), database());        childModel->setTable(relation.rel.tableName());        childModel->select();        d->relations[column].model = childModel;    }    return childModel;}/*!    \reimp*/void QSqlRelationalTableModel::revertRow(int row){    Q_D(QSqlRelationalTableModel);    for (int i = 0; i < d->relations.count(); ++i)        d->relations[i].displayValues.remove(row);    QSqlTableModel::revertRow(row);}/*!    \reimp*/void QSqlRelationalTableModel::clear(){    Q_D(QSqlRelationalTableModel);    d->clearChanges();    d->relations.clear();    QSqlTableModel::clear();}/*!    \reimp*/bool QSqlRelationalTableModel::select(){    return QSqlTableModel::select();}/*!    \reimp*/void QSqlRelationalTableModel::setTable(const QString &table){    Q_D(QSqlRelationalTableModel);    // memorize the table before applying the relations    d->baseRec = d->db.record(table);    QSqlTableModel::setTable(table);}/*! \internal */void QSqlRelationalTableModelPrivate::translateFieldNames(int row, QSqlRecord &values) const{    Q_Q(const QSqlRelationalTableModel);    for (int i = 0; i < values.count(); ++i) {        int realCol = q->indexInQuery(q->createIndex(row, i)).column();        if (realCol != -1 && relations.value(realCol).rel.isValid()) {            QVariant v = values.value(i);            values.replace(i, baseRec.field(realCol));            values.setValue(i, v);        }    }}/*!    \reimp*/bool QSqlRelationalTableModel::updateRowInTable(int row, const QSqlRecord &values){    Q_D(QSqlRelationalTableModel);    QSqlRecord rec = values;    d->translateFieldNames(row, rec);    return QSqlTableModel::updateRowInTable(row, rec);}/*!    \reimp*/bool QSqlRelationalTableModel::insertRowIntoTable(const QSqlRecord &values){    Q_D(QSqlRelationalTableModel);    QSqlRecord rec = values;    d->translateFieldNames(0, rec);    return QSqlTableModel::insertRowIntoTable(rec);}/*!    \reimp*/QString QSqlRelationalTableModel::orderByClause() const{    Q_D(const QSqlRelationalTableModel);    const QSqlRelation rel = d->relations.value(d->sortColumn).rel;    if (!rel.isValid())        return QSqlTableModel::orderByClause();    QString s = QLatin1String("ORDER BY ");    s.append(d->escapedRelationField(QLatin1String("relTblAl_") + QString::number(d->sortColumn),                    rel.displayColumn()));    s += d->sortOrder == Qt::AscendingOrder ? QLatin1String(" ASC") : QLatin1String(" DESC");    return s;}/*!    \reimp*/bool QSqlRelationalTableModel::removeColumns(int column, int count, const QModelIndex &parent){    Q_D(QSqlRelationalTableModel);    if (parent.isValid() || column < 0 || column + count > d->rec.count())        return false;    for (int i = 0; i < count; ++i) {        d->baseRec.remove(column);        if (d->relations.count() > column)            d->relations.remove(column);    }    return QSqlTableModel::removeColumns(column, count, parent);}