Using sql database from Qt
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#include <QtGui>
#include <QtSql>
#include <iostream>
using namespace std;
QString tr(const char *text)
{
return QApplication::translate(text, text);
}
void QSqlDatabase_snippets()
{
{
QSqlDatabase db = QSqlDatabase::addDatabase("QPSQL");
db.setHostName("acidalia");
db.setDatabaseName("customdb");
db.setUserName("mojito");
db.setPassword("J0a1m8");
bool ok = db.open();
Q_UNUSED(ok);
}
{
QSqlDatabase db = QSqlDatabase::database();
}
}
void QSqlField_snippets()
{
#if 0
{
QSqlField field("age", QVariant::Int);
field.setValue(QPixmap()); // WRONG
}
#endif
{
QSqlField field("age", QVariant::Int);
field.setValue(QString("123")); // casts QString to int
}
{
QSqlQuery query;
QSqlRecord record = query.record();
QSqlField field = record.field("country");
}
}
void doSomething(const QString &)
{
}
void QSqlQuery_snippets()
{
{
// typical loop
QSqlQuery query("SELECT country FROM artist");
while (query.next()) {
QString country = query.value(0).toString();
doSomething(country);
}
}
{
// field index lookup
QSqlQuery query("SELECT * FROM artist");
int fieldNo = query.record().indexOf("country");
while (query.next()) {
QString country = query.value(fieldNo).toString();
doSomething(country);
}
}
{
// named with named
QSqlQuery query;
query.prepare("INSERT INTO person (id, forename, surname) "
"VALUES (:id, :forename, :surname)");
query.bindValue(":id", 1001);
query.bindValue(":forename", "Bart");
query.bindValue(":surname", "Simpson");
query.exec();
}
{
// positional with named
QSqlQuery query;
query.prepare("INSERT INTO person (id, forename, surname) "
"VALUES (:id, :forename, :surname)");
query.bindValue(0, 1001);
query.bindValue(1, "Bart");
query.bindValue(2, "Simpson");
query.exec();
}
{
// positional 1
QSqlQuery query;
query.prepare("INSERT INTO person (id, forename, surname) "
"VALUES (?, ?, ?)");
query.bindValue(0, 1001);
query.bindValue(1, "Bart");
query.bindValue(2, "Simpson");
query.exec();
}
{
// positional 2
QSqlQuery query;
query.prepare("INSERT INTO person (id, forename, surname) "
"VALUES (?, ?, ?)");
query.addBindValue(1001);
query.addBindValue("Bart");
query.addBindValue("Simpson");
query.exec();
}
{
// stored
QSqlQuery query;
query.prepare("CALL AsciiToInt(?, ?)");
query.bindValue(0, "A");
query.bindValue(1, 0, QSql::Out);
query.exec();
int i = query.boundValue(1).toInt(); // i is 65
Q_UNUSED(i);
}
QSqlQuery query;
{
// examine with named binding
QMapIterator<QString, QVariant> i(query.boundValues());
while (i.hasNext()) {
i.next();
cout << i.key().toAscii().data() << ": "
<< i.value().toString().toAscii().data() << endl;
}
}
{
// examine with positional binding
QList<QVariant> list = query.boundValues().values();
for (int i = 0; i < list.size(); ++i)
cout << i << ": " << list.at(i).toString().toAscii().data() << endl;
}
}
void QSqlQueryModel_snippets()
{
{
QSqlQueryModel *model = new QSqlQueryModel;
model->setQuery("SELECT name, salary FROM employee");
model->setHeaderData(0, Qt::Horizontal, tr("Name"));
model->setHeaderData(1, Qt::Horizontal, tr("Salary"));
QTableView *view = new QTableView;
view->setModel(model);
view->show();
view->setEditTriggers(QAbstractItemView::NoEditTriggers);
}
QSqlQueryModel model;
model.setQuery("SELECT * FROM employee");
int salary = model.record(4).value("salary").toInt();
Q_UNUSED(salary);
{
int salary = model.data(model.index(4, 2)).toInt();
Q_UNUSED(salary);
}
for (int row = 0; row < model.rowCount(); ++row) {
for (int col = 0; col < model.columnCount(); ++col) {
qDebug() << model.data(model.index(row, col));
}
}
}
class MyModel : public QSqlQueryModel
{
public:
QVariant data(const QModelIndex &item, int role) const;
int m_specialColumnNo;
};
QVariant MyModel::data(const QModelIndex &item, int role) const
{
if (item.column() == m_specialColumnNo) {
// handle column separately
}
return QSqlQueryModel::data(item, role);
}
void QSqlTableModel_snippets()
{
QSqlTableModel *model = new QSqlTableModel;
model->setTable("employee");
model->setEditStrategy(QSqlTableModel::OnManualSubmit);
model->select();
model->removeColumn(0); // don't show the ID
model->setHeaderData(0, Qt::Horizontal, tr("Name"));
model->setHeaderData(1, Qt::Horizontal, tr("Salary"));
QTableView *view = new QTableView;
view->setModel(model);
view->show();
{
QSqlTableModel model;
model.setTable("employee");
QString name = model.record(4).value("name").toString();
}
}
void sql_intro_snippets()
{
{
QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
db.setHostName("bigblue");
db.setDatabaseName("flightdb");
db.setUserName("acarlson");
db.setPassword("1uTbSbAs");
bool ok = db.open();
Q_UNUSED(ok);
}
{
QSqlDatabase firstDB = QSqlDatabase::addDatabase("QMYSQL", "first");
QSqlDatabase secondDB = QSqlDatabase::addDatabase("QMYSQL", "second");
}
{
QSqlDatabase defaultDB = QSqlDatabase::database();
QSqlDatabase firstDB = QSqlDatabase::database("first");
QSqlDatabase secondDB = QSqlDatabase::database("second");
}
{
// SELECT1
QSqlQuery query;
query.exec("SELECT name, salary FROM employee WHERE salary > 50000");
while (query.next()) {
QString name = query.value(0).toString();
int salary = query.value(1).toInt();
qDebug() << name << salary;
}
}
{
// FEATURE
QSqlQuery query;
int numRows;
query.exec("SELECT name, salary FROM employee WHERE salary > 50000");
QSqlDatabase defaultDB = QSqlDatabase::database();
if (defaultDB.driver()->hasFeature(QSqlDriver::QuerySize)) {
numRows = query.size();
} else {
// this can be very slow
query.last();
numRows = query.at() + 1;
}
}
{
// INSERT1
QSqlQuery query;
query.exec("INSERT INTO employee (id, name, salary) "
"VALUES (1001, 'Thad Beaumont', 65000)");
}
{
// NAMED BINDING
QSqlQuery query;
query.prepare("INSERT INTO employee (id, name, salary) "
"VALUES (:id, :name, :salary)");
query.bindValue(":id", 1001);
query.bindValue(":name", "Thad Beaumont");
query.bindValue(":salary", 65000);
query.exec();
}
{
// POSITIONAL BINDING
QSqlQuery query;
query.prepare("INSERT INTO employee (id, name, salary) "
"VALUES (?, ?, ?)");
query.addBindValue(1001);
query.addBindValue("Thad Beaumont");
query.addBindValue(65000);
query.exec();
}
{
// UPDATE1
QSqlQuery query;
query.exec("UPDATE employee SET salary = 70000 WHERE id = 1003");
}
{
// DELETE1
QSqlQuery query;
query.exec("DELETE FROM employee WHERE id = 1007");
}
{
// TRANSACTION
QSqlDatabase::database().transaction();
QSqlQuery query;
query.exec("SELECT id FROM employee WHERE name = 'Torild Halvorsen'");
if (query.next()) {
int employeeId = query.value(0).toInt();
query.exec("INSERT INTO project (id, name, ownerid) "
"VALUES (201, 'Manhattan Project', "
+ QString::number(employeeId) + ')');
}
QSqlDatabase::database().commit();
}
{
// SQLQUERYMODEL1
QSqlQueryModel model;
model.setQuery("SELECT * FROM employee");
for (int i = 0; i < model.rowCount(); ++i) {
int id = model.record(i).value("id").toInt();
QString name = model.record(i).value("name").toString();
qDebug() << id << name;
}
}
{
// SQLTABLEMODEL1
QSqlTableModel model;
model.setTable("employee");
model.setFilter("salary > 50000");
model.setSort(2, Qt::DescendingOrder);
model.select();
for (int i = 0; i < model.rowCount(); ++i) {
QString name = model.record(i).value("name").toString();
int salary = model.record(i).value("salary").toInt();
qDebug() << name << salary;
}
}
{
// SQLTABLEMODEL2
QSqlTableModel model;
model.setTable("employee");
for (int i = 0; i < model.rowCount(); ++i) {
QSqlRecord record = model.record(i);
double salary = record.value("salary").toInt();
salary *= 1.1;
record.setValue("salary", salary);
model.setRecord(i, record);
}
model.submitAll();
// SQLTABLEMODEL3
int row = 1;
int column = 2;
model.setData(model.index(row, column), 75000);
model.submitAll();
// SQLTABLEMODEL4
model.insertRows(row, 1);
model.setData(model.index(row, 0), 1013);
model.setData(model.index(row, 1), "Peter Gordon");
model.setData(model.index(row, 2), 68500);
model.submitAll();
model.removeRows(row, 5);
model.submitAll();
}
}
class XyzResult : public QSqlResult
{
public:
XyzResult(const QSqlDriver *driver)
: QSqlResult(driver) {}
~XyzResult() {}
protected:
QVariant data(int /* index */) { return QVariant(); }
bool isNull(int /* index */) { return false; }
bool reset(const QString & /* query */) { return false; }
bool fetch(int /* index */) { return false; }
bool fetchFirst() { return false; }
bool fetchLast() { return false; }
int size() { return 0; }
int numRowsAffected() { return 0; }
QSqlRecord record() const { return QSqlRecord(); }
};
class XyzDriver : public QSqlDriver
{
public:
XyzDriver() {}
~XyzDriver() {}
bool hasFeature(DriverFeature /* feature */) const { return false; }
bool open(const QString & /* db */, const QString & /* user */,
const QString & /* password */, const QString & /* host */,
int /* port */, const QString & /* options */)
{ return false; }
void close() {}
QSqlResult *createResult() const { return new XyzResult(this); }
};
int main(int argc, char **argv)
{
QApplication app(argc, argv);
QSqlDatabase_snippets();
QSqlField_snippets();
QSqlQuery_snippets();
QSqlQueryModel_snippets();
QSqlTableModel_snippets();
XyzDriver driver;
XyzResult result(&driver);
}
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