QtSqlQueryModel removeRow's problem

[qtman]

hi guys,I had to ask for help.thanks advance!
my problem is the removeRow method in mycode never succeed:

QSqlQueryModel *model;
model->setQuery("select * from person");
QTableView *view = new QTableView;
view->setModel(model);

QSqlQueryModel *model;
model->setQuery("select * from person");
QTableView *view = new QTableView;
view->setModel(model);

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ok,I can get 7 rows from the person table.
now I try

model->removeRow(0);
model->removeRow(1);
...

model->removeRow(0);
model->removeRow(1);
...

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however，It donse't work。everything in the view still stay.

but if I use the flowing code:

QSqlRelationalTableModel plainModel; 
plainModel.setTable("person");
plainModel.select();
QTableView *view = new QTableView;
view->setModel(&plaiModel);
 
plainModel.removeRow(0);

QSqlRelationalTableModel plainModel; 
plainModel.setTable("person");
plainModel.select();
QTableView *view = new QTableView;
view->setModel(&plaiModel);

plainModel.removeRow(0);

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Ok,It works. there is 6 rows left in the view.

so ,whats my problem in my first case? how can i resolve it?
need i change any thing from QSqlQueryModel to QSqlRelationTableModel?
but I would like to use setQuery method than setTable method.

so ,give a help ,please.

thx