SQL examples: code cleanup

Misc code cleanup for the sql examples:
 - don't include global Qt headers but only needed ones
 - use proper tr() where possible
 - pass parameters by const ref
 - style fixes

Change-Id: I4fd4293948918b9d7b373b6d1e8eeecf6f25a622
Reviewed-by: Samuel Gaist <samuel.gaist@idiap.ch>

19 files changed, 172 insertions, 129 deletions

diff --git a/examples/sql/books/bookdelegate.cpp b/examples/sql/books/bookdelegate.cpp
index 6aac70b860..ead9f9e7db 100644
--- a/examples/sql/books/bookdelegate.cpp
+++ b/examples/sql/books/bookdelegate.cpp
@@ -3,14 +3,13 @@
 
 #include "bookdelegate.h"
 
-#include <QtWidgets>
+#include <QMouseEvent>
+#include <QPainter>
+#include <QSpinBox>
 
-BookDelegate::BookDelegate(QObject *parent)
-    : QSqlRelationalDelegate(parent)
-{}
-
-void BookDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option,
-                           const QModelIndex &index) const
+void BookDelegate::paint(QPainter *painter,
+                         const QStyleOptionViewItem &option,
+                         const QModelIndex &index) const
 {
     if (index.column() != 5) {
         QSqlRelationalDelegate::paint(painter, option, index);
@@ -38,18 +37,17 @@ void BookDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option,
         QIcon starFilledIcon(QStringLiteral(":images/star-filled.svg"));
 
         for (int i = 0; i < 5; ++i) {
-            if (i < rating) {
+            if (i < rating)
                 starFilledIcon.paint(painter, QRect(x, y, width, height));
-            } else {
+            else
                 starIcon.paint(painter, QRect(x, y, width, height));
-            }
             x += width;
         }
     }
 }
 
 QSize BookDelegate::sizeHint(const QStyleOptionViewItem &option,
-                                 const QModelIndex &index) const
+                             const QModelIndex &index) const
 {
     if (index.column() == 5)
         return QSize(5 * iconDimension, iconDimension) + QSize(cellPadding, cellPadding);
@@ -66,7 +64,7 @@ bool BookDelegate::editorEvent(QEvent *event, QAbstractItemModel *model,
 
     if (event->type() == QEvent::MouseButtonPress) {
         QMouseEvent *mouseEvent = static_cast<QMouseEvent*>(event);
-        int stars = qBound(0, int(0.7 + qreal(mouseEvent->position().toPoint().x()
+        int stars = qBound(0, int(0.7 + qreal(mouseEvent->position().x()
             - option.rect.x()) / iconDimension), 5);
         model->setData(index, QVariant(stars));
         // So that the selection can change:
diff --git a/examples/sql/books/bookdelegate.h b/examples/sql/books/bookdelegate.h
index 5ddb635515..b36cb371ac 100644
--- a/examples/sql/books/bookdelegate.h
+++ b/examples/sql/books/bookdelegate.h
@@ -5,7 +5,6 @@
 #define BOOKDELEGATE_H
 
 #include <QModelIndex>
-#include <QPixmap>
 #include <QSize>
 #include <QSqlRelationalDelegate>
 
@@ -14,7 +13,7 @@ QT_FORWARD_DECLARE_CLASS(QPainter)
 class BookDelegate : public QSqlRelationalDelegate
 {
 public:
-    BookDelegate(QObject *parent);
+    using QSqlRelationalDelegate::QSqlRelationalDelegate;
 
     void paint(QPainter *painter, const QStyleOptionViewItem &option,
                const QModelIndex &index) const override;
diff --git a/examples/sql/books/bookwindow.cpp b/examples/sql/books/bookwindow.cpp
index 8b34bd7a77..6de2d5e80a 100644
--- a/examples/sql/books/bookwindow.cpp
+++ b/examples/sql/books/bookwindow.cpp
@@ -5,16 +5,27 @@
 #include "bookdelegate.h"
 #include "initdb.h"
 
-#include <QtSql>
+#include <QApplication>
+#include <QComboBox>
+#include <QDataWidgetMapper>
+#include <QGridLayout>
+#include <QHeaderView>
+#include <QLabel>
+#include <QLineEdit>
+#include <QMenu>
+#include <QMenuBar>
+#include <QMessageBox>
+#include <QPainter>
+#include <QScrollBar>
+#include <QSpinBox>
+#include <QSqlDatabase>
+#include <QTableView>
 
 BookWindow::BookWindow()
 {
     if (!QSqlDatabase::drivers().contains("QSQLITE"))
-        QMessageBox::critical(
-                    this,
-                    "Unable to load database",
-                    "This demo needs the SQLITE driver"
-                    );
+        QMessageBox::critical(this, tr("Unable to load database"),
+                              tr("This demo needs the SQLITE driver"));
 
     // Initialize the database:
     QSqlError err = initDb();
@@ -50,8 +61,8 @@ BookWindow::BookWindow()
 
 void BookWindow::showError(const QSqlError &err)
 {
-    QMessageBox::critical(this, "Unable to initialize Database",
-                "Error initializing database: " + err.text());
+    QMessageBox::critical(this, tr("Unable to initialize Database"),
+                          tr("Error initializing database: %1").arg(err.text()));
 }
 
 void BookWindow::createLayout()
diff --git a/examples/sql/books/bookwindow.h b/examples/sql/books/bookwindow.h
index 03d83e219d..46d3570df1 100644
--- a/examples/sql/books/bookwindow.h
+++ b/examples/sql/books/bookwindow.h
@@ -4,8 +4,15 @@
 #ifndef BOOKWINDOW_H
 #define BOOKWINDOW_H
 
-#include <QtWidgets>
-#include <QtSql>
+#include <QMainWindow>
+QT_FORWARD_DECLARE_CLASS(QComboBox)
+QT_FORWARD_DECLARE_CLASS(QGridLayout)
+QT_FORWARD_DECLARE_CLASS(QLabel)
+QT_FORWARD_DECLARE_CLASS(QLineEdit)
+QT_FORWARD_DECLARE_CLASS(QSpinBox)
+QT_FORWARD_DECLARE_CLASS(QSqlError)
+QT_FORWARD_DECLARE_CLASS(QSqlRelationalTableModel)
+QT_FORWARD_DECLARE_CLASS(QTableView)
 
 class BookWindow: public QMainWindow
 {
diff --git a/examples/sql/books/initdb.h b/examples/sql/books/initdb.h
index 38fc9aeb71..9de8845a2f 100644
--- a/examples/sql/books/initdb.h
+++ b/examples/sql/books/initdb.h
@@ -4,7 +4,9 @@
 #ifndef INITDB_H
 #define INITDB_H
 
-#include <QtSql>
+#include <QDate>
+#include <QSqlError>
+#include <QSqlQuery>
 
 void addBook(QSqlQuery &q, const QString &title, int year, const QVariant &authorId,
              const QVariant &genreId, int rating)
diff --git a/examples/sql/books/main.cpp b/examples/sql/books/main.cpp
index e65ac93642..76a05f1c39 100644
--- a/examples/sql/books/main.cpp
+++ b/examples/sql/books/main.cpp
@@ -3,7 +3,7 @@
 
 #include "bookwindow.h"
 
-#include <QtWidgets>
+#include <QApplication>
 
 int main(int argc, char * argv[])
 {
diff --git a/examples/sql/cachedtable/tableeditor.cpp b/examples/sql/cachedtable/tableeditor.cpp
index 97b3fa0d96..b92e256438 100644
--- a/examples/sql/cachedtable/tableeditor.cpp
+++ b/examples/sql/cachedtable/tableeditor.cpp
@@ -1,11 +1,16 @@
 // Copyright (C) 2016 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 
-#include <QtWidgets>
-#include <QtSql>
-
 #include "tableeditor.h"
 
+#include <QDialogButtonBox>
+#include <QHBoxLayout>
+#include <QMessageBox>
+#include <QPushButton>
+#include <QSqlError>
+#include <QSqlTableModel>
+#include <QTableView>
+
 //! [0]
 TableEditor::TableEditor(const QString &tableName, QWidget *parent)
     : QWidget(parent)
diff --git a/examples/sql/cachedtable/tableeditor.h b/examples/sql/cachedtable/tableeditor.h
index dfa50a8934..8c3c56b397 100644
--- a/examples/sql/cachedtable/tableeditor.h
+++ b/examples/sql/cachedtable/tableeditor.h
@@ -6,11 +6,9 @@
 
 #include <QDialog>
 
-QT_BEGIN_NAMESPACE
-class QDialogButtonBox;
-class QPushButton;
-class QSqlTableModel;
-QT_END_NAMESPACE
+QT_FORWARD_DECLARE_CLASS(QDialogButtonBox)
+QT_FORWARD_DECLARE_CLASS(QPushButton)
+QT_FORWARD_DECLARE_CLASS(QSqlTableModel)
 
 //! [0]
 class TableEditor : public QWidget
diff --git a/examples/sql/masterdetail/dialog.cpp b/examples/sql/masterdetail/dialog.cpp
index 19e941af30..0b8ed8a75b 100644
--- a/examples/sql/masterdetail/dialog.cpp
+++ b/examples/sql/masterdetail/dialog.cpp
@@ -3,10 +3,23 @@
 
 #include "dialog.h"
 
-int uniqueAlbumId;
-int uniqueArtistId;
-
-Dialog::Dialog(QSqlRelationalTableModel *albums, QDomDocument details,
+#include <QDialogButtonBox>
+#include <QDate>
+#include <QDomDocument>
+#include <QGroupBox>
+#include <QLabel>
+#include <QLineEdit>
+#include <QMessageBox>
+#include <QPushButton>
+#include <QSpinBox>
+#include <QSqlField>
+#include <QSqlRelationalTableModel>
+#include <QSqlRecord>
+#include <QVBoxLayout>
+
+int Dialog::s_artistId = 0;
+int Dialog::s_albumId = 0;
+Dialog::Dialog(QSqlRelationalTableModel *albums, const QDomDocument &details,
                QFile *output, QWidget *parent)
      : QDialog(parent)
 {
@@ -25,6 +38,12 @@ Dialog::Dialog(QSqlRelationalTableModel *albums, QDomDocument details,
     setWindowTitle(tr("Add Album"));
 }
 
+void Dialog::setInitialAlbumAndArtistId(int albumId, int artistId)
+{
+    s_albumId = albumId;
+    s_artistId = artistId;
+}
+
 void Dialog::submit()
 {
     QString artist = artistEditor->text();
@@ -145,7 +164,7 @@ void Dialog::addTracks(int albumId, const QStringList &tracks)
 */
 }
 
-void Dialog::increaseAlbumCount(QModelIndex artistIndex)
+void Dialog::increaseAlbumCount(const QModelIndex &artistIndex)
 {
     QSqlTableModel *artistModel = model->relationModel(2);
 
@@ -219,7 +238,7 @@ QDialogButtonBox *Dialog::createButtons()
     return buttonBox;
 }
 
-QModelIndex Dialog::indexOfArtist(const QString &artist)
+QModelIndex Dialog::indexOfArtist(const QString &artist) const
 {
     QSqlTableModel *artistModel = model->relationModel(2);
 
@@ -234,12 +253,12 @@ QModelIndex Dialog::indexOfArtist(const QString &artist)
 
 int Dialog::generateArtistId()
 {
-    uniqueArtistId += 1;
-    return uniqueArtistId;
+    s_artistId += 1;
+    return s_artistId;
 }
 
 int Dialog::generateAlbumId()
 {
-    uniqueAlbumId += 1;
-    return uniqueAlbumId;
+    s_albumId += 1;
+    return s_albumId;
 }
diff --git a/examples/sql/masterdetail/dialog.h b/examples/sql/masterdetail/dialog.h
index 0c5a728ebb..2a4f5a0b8e 100644
--- a/examples/sql/masterdetail/dialog.h
+++ b/examples/sql/masterdetail/dialog.h
@@ -4,17 +4,25 @@
 #ifndef DIALOG_H
 #define DIALOG_H
 
-#include <QtWidgets>
-#include <QtSql>
-#include <QtXml>
+#include <QDialog>
+#include <QDomDocument>
+
+QT_FORWARD_DECLARE_CLASS(QDialogButtonBox)
+QT_FORWARD_DECLARE_CLASS(QFile)
+QT_FORWARD_DECLARE_CLASS(QGroupBox)
+QT_FORWARD_DECLARE_CLASS(QLineEdit)
+QT_FORWARD_DECLARE_CLASS(QModelIndex)
+QT_FORWARD_DECLARE_CLASS(QSpinBox)
+QT_FORWARD_DECLARE_CLASS(QSqlRelationalTableModel)
 
 class Dialog : public QDialog
 {
     Q_OBJECT
 
 public:
-    Dialog(QSqlRelationalTableModel *albums, QDomDocument details,
+    Dialog(QSqlRelationalTableModel *albums, const QDomDocument &details,
            QFile *output, QWidget *parent = nullptr);
+    static void setInitialAlbumAndArtistId(int albumId, int artistId);
 
 private slots:
     void revert();
@@ -27,10 +35,8 @@ private:
     QDialogButtonBox *createButtons();
     QGroupBox *createInputWidgets();
     int findArtistId(const QString &artist);
-    static int generateAlbumId();
-    static int generateArtistId();
-    void increaseAlbumCount(QModelIndex artistIndex);
-    QModelIndex indexOfArtist(const QString &artist);
+    void increaseAlbumCount(const QModelIndex &artistIndex);
+    QModelIndex indexOfArtist(const QString &artist) const;
 
     QSqlRelationalTableModel *model;
     QDomDocument albumDetails;
@@ -40,6 +46,11 @@ private:
     QLineEdit *titleEditor;
     QSpinBox *yearEditor;
     QLineEdit *tracksEditor;
+
+    static int generateAlbumId();
+    static int generateArtistId();
+    static int s_artistId;
+    static int s_albumId;
 };
 
 #endif
diff --git a/examples/sql/masterdetail/main.cpp b/examples/sql/masterdetail/main.cpp
index e99d8e8645..50d99cf24e 100644
--- a/examples/sql/masterdetail/main.cpp
+++ b/examples/sql/masterdetail/main.cpp
@@ -7,8 +7,6 @@
 #include <QApplication>
 #include <QFile>
 
-#include <stdlib.h>
-
 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);
diff --git a/examples/sql/masterdetail/mainwindow.cpp b/examples/sql/masterdetail/mainwindow.cpp
index d720db1033..020a149b22 100644
--- a/examples/sql/masterdetail/mainwindow.cpp
+++ b/examples/sql/masterdetail/mainwindow.cpp
@@ -4,12 +4,20 @@
 #include "mainwindow.h"
 #include "dialog.h"
 
-#include <QtWidgets>
-#include <QtSql>
-#include <QtXml>
-
-extern int uniqueAlbumId;
-extern int uniqueArtistId;
+#include <QApplication>
+#include <QComboBox>
+#include <QHeaderView>
+#include <QFile>
+#include <QGridLayout>
+#include <QGroupBox>
+#include <QLabel>
+#include <QListWidget>
+#include <QMenu>
+#include <QMenuBar>
+#include <QMessageBox>
+#include <QSqlRecord>
+#include <QSqlRelationalTableModel>
+#include <QTableView>
 
 MainWindow::MainWindow(const QString &artistTable, const QString &albumTable,
                        QFile *albumDetails, QWidget *parent)
@@ -28,13 +36,12 @@ MainWindow::MainWindow(const QString &artistTable, const QString &albumTable,
     QGroupBox *details = createDetailsGroupBox();
 
     artistView->setCurrentIndex(0);
-    uniqueAlbumId = model->rowCount();
-    uniqueArtistId = artistView->count();
+    Dialog::setInitialAlbumAndArtistId(model->rowCount(), artistView->count());
 
     connect(model, &QSqlRelationalTableModel::rowsInserted,
-            this, &MainWindow::updateHeader);
+            this, &MainWindow::adjustHeader);
     connect(model, &QSqlRelationalTableModel::rowsRemoved,
-            this, &MainWindow::updateHeader);
+            this, &MainWindow::adjustHeader);
 
     QGridLayout *layout = new QGridLayout;
     layout->addWidget(artists, 0, 0);
@@ -67,7 +74,7 @@ void MainWindow::changeArtist(int row)
     }
 }
 
-void MainWindow::showArtistProfile(QModelIndex index)
+void MainWindow::showArtistProfile(const QModelIndex &index)
 {
     QSqlRecord record = model->relationModel(2)->record(index.row());
 
@@ -84,7 +91,7 @@ void MainWindow::showArtistProfile(QModelIndex index)
     imageLabel->hide();
 }
 
-void MainWindow::showAlbumDetails(QModelIndex index)
+void MainWindow::showAlbumDetails(const QModelIndex &index)
 {
     QSqlRecord record = model->record(index.row());
 
@@ -113,14 +120,11 @@ void MainWindow::getTrackList(QDomNode album)
 {
     trackList->clear();
 
-    QDomNodeList tracks = album.childNodes();
-    QDomNode track;
-    QString trackNumber;
-
+    const QDomNodeList tracks = album.childNodes();
     for (int i = 0; i < tracks.count(); ++i) {
 
-        track = tracks.item(i);
-        trackNumber = track.toElement().attribute("number");
+        const QDomNode track = tracks.item(i);
+        const QString trackNumber = track.toElement().attribute("number");
 
         QListWidgetItem *item = new QListWidgetItem(trackList);
         item->setText(trackNumber + ": " + track.toElement().text());
@@ -132,7 +136,7 @@ void MainWindow::addAlbum()
     Dialog *dialog = new Dialog(model, albumData, file, this);
     int accepted = dialog->exec();
 
-    if (accepted == 1) {
+    if (accepted == QDialog::Accepted) {
         int lastRow = model->rowCount() - 1;
         albumView->selectRow(lastRow);
         albumView->scrollToBottom();
@@ -142,10 +146,10 @@ void MainWindow::addAlbum()
 
 void MainWindow::deleteAlbum()
 {
-    QModelIndexList selection = albumView->selectionModel()->selectedRows(0);
+    const QModelIndexList selection = albumView->selectionModel()->selectedRows(0);
 
     if (!selection.empty()) {
-        QModelIndex idIndex = selection.at(0);
+        const QModelIndex &idIndex = selection.at(0);
         int id = idIndex.data().toInt();
         QString title = idIndex.sibling(idIndex.row(), 1).data().toString();
         QString artist = idIndex.sibling(idIndex.row(), 2).data().toString();
@@ -172,9 +176,7 @@ void MainWindow::deleteAlbum()
 
 void MainWindow::removeAlbumFromFile(int id)
 {
-
     QDomNodeList albums = albumData.elementsByTagName("album");
-
     for (int i = 0; i < albums.count(); ++i) {
         QDomNode node = albums.item(i);
         if (node.toElement().attribute("id").toInt() == id) {
@@ -197,12 +199,12 @@ void MainWindow::removeAlbumFromFile(int id)
 */
 }
 
-void MainWindow::removeAlbumFromDatabase(QModelIndex index)
+void MainWindow::removeAlbumFromDatabase(const QModelIndex &index)
 {
     model->removeRow(index.row());
 }
 
-void MainWindow::decreaseAlbumCount(QModelIndex artistIndex)
+void MainWindow::decreaseAlbumCount(const QModelIndex &artistIndex)
 {
     int row = artistIndex.row();
     QModelIndex albumCountIndex = artistIndex.sibling(row, 2);
@@ -358,7 +360,7 @@ void MainWindow::showImageLabel()
     imageLabel->show();
 }
 
-QModelIndex MainWindow::indexOfArtist(const QString &artist)
+QModelIndex MainWindow::indexOfArtist(const QString &artist) const
 {
     QSqlTableModel *artistModel = model->relationModel(2);
 
@@ -370,11 +372,6 @@ QModelIndex MainWindow::indexOfArtist(const QString &artist)
     return QModelIndex();
 }
 
-void MainWindow::updateHeader(QModelIndex, int, int)
-{
-    adjustHeader();
-}
-
 void MainWindow::adjustHeader()
 {
     albumView->hideColumn(0);
diff --git a/examples/sql/masterdetail/mainwindow.h b/examples/sql/masterdetail/mainwindow.h
index a5f9e70648..cc2a5c9f59 100644
--- a/examples/sql/masterdetail/mainwindow.h
+++ b/examples/sql/masterdetail/mainwindow.h
@@ -8,15 +8,13 @@
 #include <QMainWindow>
 #include <QModelIndex>
 
-QT_BEGIN_NAMESPACE
-class QComboBox;
-class QFile;
-class QGroupBox;
-class QLabel;
-class QListWidget;
-class QSqlRelationalTableModel;
-class QTableView;
-QT_END_NAMESPACE
+QT_FORWARD_DECLARE_CLASS(QComboBox)
+QT_FORWARD_DECLARE_CLASS(QFile)
+QT_FORWARD_DECLARE_CLASS(QGroupBox)
+QT_FORWARD_DECLARE_CLASS(QLabel)
+QT_FORWARD_DECLARE_CLASS(QListWidget)
+QT_FORWARD_DECLARE_CLASS(QSqlRelationalTableModel)
+QT_FORWARD_DECLARE_CLASS(QTableView)
 
 class MainWindow : public QMainWindow
 {
@@ -31,21 +29,20 @@ private slots:
     void addAlbum();
     void changeArtist(int row);
     void deleteAlbum();
-    void showAlbumDetails(QModelIndex index);
-    void showArtistProfile(QModelIndex index);
-    void updateHeader(QModelIndex, int, int);
+    void showAlbumDetails(const QModelIndex &index);
+    void showArtistProfile(const QModelIndex &index);
+    void adjustHeader();
 
 private:
-    void adjustHeader();
     QGroupBox *createAlbumGroupBox();
     QGroupBox *createArtistGroupBox();
     QGroupBox *createDetailsGroupBox();
     void createMenuBar();
-    void decreaseAlbumCount(QModelIndex artistIndex);
+    void decreaseAlbumCount(const QModelIndex &artistIndex);
     void getTrackList(QDomNode album);
-    QModelIndex indexOfArtist(const QString &artist);
+    QModelIndex indexOfArtist(const QString &artist) const;
     void readAlbumData();
-    void removeAlbumFromDatabase(QModelIndex album);
+    void removeAlbumFromDatabase(const QModelIndex &album);
     void removeAlbumFromFile(int id);
     void showImageLabel();
 
diff --git a/examples/sql/querymodel/customsqlmodel.cpp b/examples/sql/querymodel/customsqlmodel.cpp
index 9063911218..e87be12f09 100644
--- a/examples/sql/querymodel/customsqlmodel.cpp
+++ b/examples/sql/querymodel/customsqlmodel.cpp
@@ -1,10 +1,10 @@
 // Copyright (C) 2016 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 
-#include <QtWidgets>
-
 #include "customsqlmodel.h"
 
+#include <QColor>
+
 CustomSqlModel::CustomSqlModel(QObject *parent)
     : QSqlQueryModel(parent)
 {
diff --git a/examples/sql/querymodel/editablesqlmodel.cpp b/examples/sql/querymodel/editablesqlmodel.cpp
index b7cb930020..dc91666c06 100644
--- a/examples/sql/querymodel/editablesqlmodel.cpp
+++ b/examples/sql/querymodel/editablesqlmodel.cpp
@@ -1,18 +1,17 @@
 // Copyright (C) 2016 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 
-#include <QtSql>
-
 #include "editablesqlmodel.h"
 
+#include <QSqlQuery>
+
 EditableSqlModel::EditableSqlModel(QObject *parent)
     : QSqlQueryModel(parent)
 {
 }
 
 //! [0]
-Qt::ItemFlags EditableSqlModel::flags(
-        const QModelIndex &index) const
+Qt::ItemFlags EditableSqlModel::flags(const QModelIndex &index) const
 {
     Qt::ItemFlags flags = QSqlQueryModel::flags(index);
     if (index.column() == 1 || index.column() == 2)
@@ -33,11 +32,10 @@ bool EditableSqlModel::setData(const QModelIndex &index, const QVariant &value,
     clear();
 
     bool ok;
-    if (index.column() == 1) {
+    if (index.column() == 1)
         ok = setFirstName(id, value.toString());
-    } else {
+    else
         ok = setLastName(id, value.toString());
-    }
     refresh();
     return ok;
 }
diff --git a/examples/sql/querymodel/main.cpp b/examples/sql/querymodel/main.cpp
index 8c5af768e3..a4680f7fe8 100644
--- a/examples/sql/querymodel/main.cpp
+++ b/examples/sql/querymodel/main.cpp
@@ -8,8 +8,6 @@
 #include <QApplication>
 #include <QTableView>
 
-#include <stdlib.h>
-
 void initializeModel(QSqlQueryModel *model)
 {
     model->setQuery("select * from person");
diff --git a/examples/sql/sqlwidgetmapper/window.cpp b/examples/sql/sqlwidgetmapper/window.cpp
index fee3bc78dd..cd44174f84 100644
--- a/examples/sql/sqlwidgetmapper/window.cpp
+++ b/examples/sql/sqlwidgetmapper/window.cpp
@@ -1,11 +1,20 @@
 // Copyright (C) 2016 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 
-#include <QtWidgets>
-#include <QtSql>
-
 #include "window.h"
 
+#include <QComboBox>
+#include <QDataWidgetMapper>
+#include <QGridLayout>
+#include <QLabel>
+#include <QLineEdit>
+#include <QMessageBox>
+#include <QPushButton>
+#include <QSqlQuery>
+#include <QSqlRelationalDelegate>
+#include <QSqlTableModel>
+#include <QTextEdit>
+
 //! [Set up widgets]
 Window::Window(QWidget *parent)
     : QWidget(parent)
diff --git a/examples/sql/sqlwidgetmapper/window.h b/examples/sql/sqlwidgetmapper/window.h
index c3b01155af..9af9628b90 100644
--- a/examples/sql/sqlwidgetmapper/window.h
+++ b/examples/sql/sqlwidgetmapper/window.h
@@ -6,18 +6,16 @@
 
 #include <QWidget>
 
-QT_BEGIN_NAMESPACE
-class QComboBox;
-class QDataWidgetMapper;
-class QItemSelectionModel;
-class QLabel;
-class QLineEdit;
-class QPushButton;
-class QSqlRelationalTableModel;
-class QStandardItemModel;
-class QStringListModel;
-class QTextEdit;
-QT_END_NAMESPACE
+QT_FORWARD_DECLARE_CLASS(QComboBox)
+QT_FORWARD_DECLARE_CLASS(QDataWidgetMapper)
+QT_FORWARD_DECLARE_CLASS(QItemSelectionModel)
+QT_FORWARD_DECLARE_CLASS(QLabel)
+QT_FORWARD_DECLARE_CLASS(QLineEdit)
+QT_FORWARD_DECLARE_CLASS(QPushButton)
+QT_FORWARD_DECLARE_CLASS(QSqlRelationalTableModel)
+QT_FORWARD_DECLARE_CLASS(QStandardItemModel)
+QT_FORWARD_DECLARE_CLASS(QStringListModel)
+QT_FORWARD_DECLARE_CLASS(QTextEdit)
 
 //! [Window definition]
 class Window : public QWidget
diff --git a/examples/sql/tablemodel/tablemodel.cpp b/examples/sql/tablemodel/tablemodel.cpp
index ae0aa17719..04c114dc63 100644
--- a/examples/sql/tablemodel/tablemodel.cpp
+++ b/examples/sql/tablemodel/tablemodel.cpp
@@ -6,8 +6,6 @@
 #include <QSqlTableModel>
 #include <QTableView>
 
-#include <stdlib.h>
-
 void initializeModel(QSqlTableModel *model)
 {
     model->setTable("person");