我想做的是 query.exec() 一个 DELETE 语句，如果删除成功我想显示更新的表，否则显示一个 QMessageBox 说名称不匹配。
我的印象是，如果 DELETE 语句找不到条目，query.exec() 将为 FALSE。但无论我输入什么名字，它总是正确的。有解决这个问题的方法吗？谢谢大家...
所以我目前的代码是:
bool ok;
QInputDialog *dialog = new QInputDialog;
QString name = dialog->getText((QWidget*)this->parent(), tr("Enter Buyer to Delete:"),
tr("Buyer Name:"), QLineEdit::Normal,
"", &ok);
QSqlTableModel *model1;
QSqlQuery query;
query.prepare("DELETE from buyers WHERE name=:name");
query.addBindValue(name);
bool x = query.exec(); //<----PROBLEM: EVEN WITH INCORRECT name,
qDebug() << x; // query.exec() RETURNS true ALTHOUGH delete
if (!x) // IS SUPPOSED TO FAIL
{
QMessageBox box;
box.setInformativeText("No buyer found with name matching " + name);
box.exec();
}
model1 = new QSqlTableModel;
model1->setTable("buyers");
model1->select();
model1->setHeaderData(0, Qt::Horizontal, tr("ID"));
model1->setHeaderData(1, Qt::Horizontal, tr("Name"));
model1->setHeaderData(2, Qt::Horizontal, tr("Location"));
model1->setHeaderData(3, Qt::Horizontal, tr("Phone"));
model1->setHeaderData(4, Qt::Horizontal, tr("Email"));
QTableView *view1 = new QTableView;
view1->setWindowTitle("Buyer List updated");
view1->setModel(model1);
view1->show();
最佳答案
您可以使用QSqlQuery::numRowsAffected():
QSqlQuery query("your_query_here");
query.exec();
if(query.numRowsAffected() == 0)
{
//didn't delete anything
}
else
{
//worked fine
}
注意，根据 Qt 文档，这个函数
Returns the number of rows affected by the result's SQL statement, or -1 if it cannot be determined. Note that for SELECT statements, the value is undefined; use size() instead. If the query is not active, -1 is returned.
关于c++ - Qt Creator中如何根据Sql Query结果做条件语句？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/28448088/