Connecting SQLite databse with QT

**rushanbashir** · 11th April 2013, 07:53

Hello Everyone!

I am using QT5.0 I want to know how can I establish connection between the SQLite database and QT. Below is the code for my connection. I am using a in memory database as well but I want to connect a custom database.

#include "browser.h"
#include "qsqlconnectiondialog.h"

#include <QtGui>
#include <QtSql>

Browser::Browser(QWidget *parent)
: QWidget(parent)
{
setupUi(this);

table->addAction(insertRowAction);
table->addAction(deleteRowAction);

if (QSqlDatabase::drivers().isEmpty())
QMessageBox::information(this, tr("No database drivers found"),
tr("This demo requires at least one Qt database driver. "
"Please check the documentation how to build the "
"Qt SQL plugins."));

emit statusMessage(tr("Ready."));
}

Browser::~Browser()
{
}

void Browser::exec()
{
QSqlQueryModel *model = new QSqlQueryModel(table);
model->setQuery(QSqlQuery(sqlEdit->toPlainText(), connectionWidget->currentDatabase()));
table->setModel(model);

if (model->lastError().type() != QSqlError::NoError)
emit statusMessage(model->lastError().text());
else if (model->query().isSelect())
emit statusMessage(tr("Query OK."));
else
emit statusMessage(tr("Query OK, number of affected rows: %1").arg(
model->query().numRowsAffected()));

updateActions();
}

QSqlError Browser::addConnection(const QString &driver, const QString &dbName, const QString &host,
const QString &user, const QString &passwd, int port)
{
static int cCount = 0;

QSqlError err;
QSqlDatabase db = QSqlDatabase::addDatabase(driver, QString("Browser%1").arg(++cCount));
db.setDatabaseName(dbName);
db.setHostName(host);
db.setPort(port);
if (!db.open(user, passwd)) {
err = db.lastError();
db = QSqlDatabase();
QSqlDatabase::removeDatabase(QString("Browser%1"). arg(cCount));
}
connectionWidget->refresh();

return err;
}

void Browser::addConnection()
{
QSqlConnectionDialog dialog(this);
if (dialog.exec() != QDialog::Accepted)
return;

if (dialog.useInMemoryDatabase()) {
QSqlDatabase::database("in_mem_db", false).close();
QSqlDatabase::removeDatabase("in_mem_db");
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE", "in_mem_db");
db.setDatabaseName(":memory:");
if (!db.open())
QMessageBox::warning(this, tr("Unable to open database"), tr("An error occurred while "
"opening the connection: ") + db.lastError().text());
QSqlQuery q("", db);
q.exec("drop table Movies");
q.exec("drop table Names");
q.exec("create table Movies (id integer primary key, Title varchar, Director varchar, Rating number)");
q.exec("insert into Movies values (0, 'Metropolis', 'Fritz Lang', '8.4')");
q.exec("insert into Movies values (1, 'Nosferatu, eine Symphonie des Grauens', 'F.W. Murnau', '8.1')");
q.exec("insert into Movies values (2, 'Bis ans Ende der Welt', 'Wim Wenders', '6.5')");
q.exec("insert into Movies values (3, 'Hardware', 'Richard Stanley', '5.2')");
q.exec("insert into Movies values (4, 'Mitchell', 'Andrew V. McLaglen', '2.1')");
q.exec("create table Names (id integer primary key, Firstname varchar, Lastname varchar, City varchar)");
q.exec("insert into Names values (0, 'Sala', 'Palmer', 'Morristown')");
q.exec("insert into Names values (1, 'Christopher', 'Walker', 'Morristown')");
q.exec("insert into Names values (2, 'Donald', 'Duck', 'Andeby')");
q.exec("insert into Names values (3, 'Buck', 'Rogers', 'Paris')");
q.exec("insert into Names values (4, 'Sherlock', 'Holmes', 'London')");
connectionWidget->refresh();
} else {
QSqlError err = addConnection(dialog.driverName(), dialog.databaseName(), dialog.hostName(),
dialog.userName(), dialog.password(), dialog.port());
if (err.type() != QSqlError::NoError)
QMessageBox::warning(this, tr("Unable to open database"), tr("An error occurred while "
"opening the connection: ") + err.text());
}
}

void Browser::showTable(const QString &t)
{
QSqlTableModel *model = new QSqlTableModel(table, connectionWidget->currentDatabase());
model->setEditStrategy(QSqlTableModel::OnRowChange);
model->setTable(connectionWidget->currentDatabase().driver()->escapeIdentifier(t, QSqlDriver::TableName));
model->select();
if (model->lastError().type() != QSqlError::NoError)
emit statusMessage(model->lastError().text());
table->setModel(model);
table->setEditTriggers(QAbstractItemView:

oubleClicked|QAbstractItemView::EditKeyPressed);

connect(table->selectionModel(), SIGNAL(currentRowChanged(QModelIndex,QModelIndex)) ,
this, SLOT(currentChanged()));
updateActions();
}

void Browser::showMetaData(const QString &t)
{
QSqlRecord rec = connectionWidget->currentDatabase().record(t);
QStandardItemModel *model = new QStandardItemModel(table);

model->insertRows(0, rec.count());
model->insertColumns(0, 7);

model->setHeaderData(0, Qt::Horizontal, "Fieldname");
model->setHeaderData(1, Qt::Horizontal, "Type");
model->setHeaderData(2, Qt::Horizontal, "Length");
model->setHeaderData(3, Qt::Horizontal, "Precision");
model->setHeaderData(4, Qt::Horizontal, "Required");
model->setHeaderData(5, Qt::Horizontal, "AutoValue");
model->setHeaderData(6, Qt::Horizontal, "DefaultValue");

for (int i = 0; i < rec.count(); ++i) {
QSqlField fld = rec.field(i);
model->setData(model->index(i, 0), fld.name());
model->setData(model->index(i, 1), fld.typeID() == -1
? QString(QVariant::typeToName(fld.type()))
: QString("%1 (%2)").arg(QVariant::typeToName(fld.type())).arg(f ld.typeID()));
model->setData(model->index(i, 2), fld.length());
model->setData(model->index(i, 3), fld.precision());
model->setData(model->index(i, 4), fld.requiredStatus() == -1 ? QVariant("?")
: QVariant(bool(fld.requiredStatus())));
model->setData(model->index(i, 5), fld.isAutoValue());
model->setData(model->index(i, 6), fld.defaultValue());
}

table->setModel(model);
table->setEditTriggers(QAbstractItemView::NoEditTriggers );

updateActions();
}

void Browser::insertRow()
{
QSqlTableModel *model = qobject_cast<QSqlTableModel *>(table->model());
if (!model)
return;

QModelIndex insertIndex = table->currentIndex();
int row = insertIndex.row() == -1 ? 0 : insertIndex.row();
model->insertRow(row);
insertIndex = model->index(row, 0);
table->setCurrentIndex(insertIndex);
table->edit(insertIndex);
}

void Browser::deleteRow()
{
QSqlTableModel *model = qobject_cast<QSqlTableModel *>(table->model());
if (!model)
return;

model->setEditStrategy(QSqlTableModel::OnManualSubmit) ;

QModelIndexList currentSelection = table->selectionModel()->selectedIndexes();
for (int i = 0; i < currentSelection.count(); ++i) {
if (currentSelection.at(i).column() != 0)
continue;
model->removeRow(currentSelection.at(i).row());
}

model->submitAll();
model->setEditStrategy(QSqlTableModel::OnRowChange);

updateActions();
}

void Browser::updateActions()
{
bool enableIns = qobject_cast<QSqlTableModel *>(table->model());
bool enableDel = enableIns && table->currentIndex().isValid();

insertRowAction->setEnabled(enableIns);
deleteRowAction->setEnabled(enableDel);
}

void Browser::about()
{
QMessageBox::about(this, tr("About"), tr("The SQL Browser demonstration "
"shows how a data browser can be used to visualize the results of SQL"
"statements on a live database"));
}

**Lesiok** · 11th April 2013, 08:01

Your mail is unreadable. First put code in tag CODE, second say what is a problem ?

**rushanbashir** · 11th April 2013, 08:16

Here is the code. I can use the pre defined database but cannot connect an external SQLite databse saved somewhere in my computer.

#include "browser.h"
#include "qsqlconnectiondialog.h"

#include <QtGui>
#include <QtSql>

Browser::Browser(QWidget *parent)
: QWidget(parent)
{
setupUi(this);

table->addAction(insertRowAction);
table->addAction(deleteRowAction);

if (QSqlDatabase::drivers().isEmpty())
QMessageBox::information(this, tr("No database drivers found"),
tr("This demo requires at least one Qt database driver. "
"Please check the documentation how to build the "
"Qt SQL plugins."));

emit statusMessage(tr("Ready."));
}

Browser::~Browser()
{
}

void Browser::exec()
{
QSqlQueryModel *model = new QSqlQueryModel(table);
model->setQuery(QSqlQuery(sqlEdit->toPlainText(), connectionWidget->currentDatabase()));
table->setModel(model);

if (model->lastError().type() != QSqlError::NoError)
emit statusMessage(model->lastError().text());
else if (model->query().isSelect())
emit statusMessage(tr("Query OK."));
else
emit statusMessage(tr("Query OK, number of affected rows: %1").arg(
model->query().numRowsAffected()));

updateActions();
}

QSqlError Browser::addConnection(const QString &driver, const QString &dbName, const QString &host,
const QString &user, const QString &passwd, int port)
{
static int cCount = 0;

QSqlError err;
QSqlDatabase db = QSqlDatabase::addDatabase(driver, QString("Browser%1").arg(++cCount));
db.setDatabaseName(dbName);
db.setHostName(host);
db.setPort(port);
if (!db.open(user, passwd)) {
err = db.lastError();
db = QSqlDatabase();
QSqlDatabase::removeDatabase(QString("Browser%1"). arg(cCount));
}
connectionWidget->refresh();

return err;
}

void Browser::addConnection()
{
QSqlConnectionDialog dialog(this);
if (dialog.exec() != QDialog::Accepted)
return;

if (dialog.useInMemoryDatabase()) {
QSqlDatabase::database("in_mem_db", false).close();
QSqlDatabase::removeDatabase("in_mem_db");
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE", "in_mem_db");
db.setDatabaseName(":memory:");
if (!db.open())
QMessageBox::warning(this, tr("Unable to open database"), tr("An error occurred while "
"opening the connection: ") + db.lastError().text());
QSqlQuery q("", db);
q.exec("drop table Movies");
q.exec("drop table Names");
q.exec("create table Movies (id integer primary key, Title varchar, Director varchar, Rating number)");
q.exec("insert into Movies values (0, 'Metropolis', 'Fritz Lang', '8.4')");
q.exec("insert into Movies values (1, 'Nosferatu, eine Symphonie des Grauens', 'F.W. Murnau', '8.1')");
q.exec("insert into Movies values (2, 'Bis ans Ende der Welt', 'Wim Wenders', '6.5')");
q.exec("insert into Movies values (3, 'Hardware', 'Richard Stanley', '5.2')");
q.exec("insert into Movies values (4, 'Mitchell', 'Andrew V. McLaglen', '2.1')");
q.exec("create table Names (id integer primary key, Firstname varchar, Lastname varchar, City varchar)");
q.exec("insert into Names values (0, 'Sala', 'Palmer', 'Morristown')");
q.exec("insert into Names values (1, 'Christopher', 'Walker', 'Morristown')");
q.exec("insert into Names values (2, 'Donald', 'Duck', 'Andeby')");
q.exec("insert into Names values (3, 'Buck', 'Rogers', 'Paris')");
q.exec("insert into Names values (4, 'Sherlock', 'Holmes', 'London')");
connectionWidget->refresh();
} else {
QSqlError err = addConnection(dialog.driverName(), dialog.databaseName(), dialog.hostName(),
dialog.userName(), dialog.password(), dialog.port());
if (err.type() != QSqlError::NoError)
QMessageBox::warning(this, tr("Unable to open database"), tr("An error occurred while "
"opening the connection: ") + err.text());
}
}

void Browser::showTable(const QString &t)
{
QSqlTableModel *model = new QSqlTableModel(table, connectionWidget->currentDatabase());
model->setEditStrategy(QSqlTableModel::OnRowChange);
model->setTable(connectionWidget->currentDatabase().driver()->escapeIdentifier(t, QSqlDriver::TableName));
model->select();
if (model->lastError().type() != QSqlError::NoError)
emit statusMessage(model->lastError().text());
table->setModel(model);
table->setEditTriggers(QAbstractItemView

ubleClicked|QAbstractItemView::EditKeyPressed);

connect(table->selectionModel(), SIGNAL(currentRowChanged(QModelIndex,QModelIndex)) ,
this, SLOT(currentChanged()));
updateActions();
}

void Browser::showMetaData(const QString &t)
{
QSqlRecord rec = connectionWidget->currentDatabase().record(t);
QStandardItemModel *model = new QStandardItemModel(table);

model->insertRows(0, rec.count());
model->insertColumns(0, 7);

model->setHeaderData(0, Qt::Horizontal, "Fieldname");
model->setHeaderData(1, Qt::Horizontal, "Type");
model->setHeaderData(2, Qt::Horizontal, "Length");
model->setHeaderData(3, Qt::Horizontal, "Precision");
model->setHeaderData(4, Qt::Horizontal, "Required");
model->setHeaderData(5, Qt::Horizontal, "AutoValue");
model->setHeaderData(6, Qt::Horizontal, "DefaultValue");

for (int i = 0; i < rec.count(); ++i) {
QSqlField fld = rec.field(i);
model->setData(model->index(i, 0), fld.name());
model->setData(model->index(i, 1), fld.typeID() == -1
? QString(QVariant::typeToName(fld.type()))
: QString("%1 (%2)").arg(QVariant::typeToName(fld.type())).arg(f ld.typeID()));
model->setData(model->index(i, 2), fld.length());
model->setData(model->index(i, 3), fld.precision());
model->setData(model->index(i, 4), fld.requiredStatus() == -1 ? QVariant("?")
: QVariant(bool(fld.requiredStatus())));
model->setData(model->index(i, 5), fld.isAutoValue());
model->setData(model->index(i, 6), fld.defaultValue());
}

table->setModel(model);
table->setEditTriggers(QAbstractItemView::NoEditTrigge rs );

updateActions();
}

void Browser::insertRow()
{
QSqlTableModel *model = qobject_cast<QSqlTableModel *>(table->model());
if (!model)
return;

QModelIndex insertIndex = table->currentIndex();
int row = insertIndex.row() == -1 ? 0 : insertIndex.row();
model->insertRow(row);
insertIndex = model->index(row, 0);
table->setCurrentIndex(insertIndex);
table->edit(insertIndex);
}

void Browser::deleteRow()
{
QSqlTableModel *model = qobject_cast<QSqlTableModel *>(table->model());
if (!model)
return;

model->setEditStrategy(QSqlTableModel::OnManualSubmit) ;

QModelIndexList currentSelection = table->selectionModel()->selectedIndexes();
for (int i = 0; i < currentSelection.count(); ++i) {
if (currentSelection.at(i).column() != 0)
continue;
model->removeRow(currentSelection.at(i).row());
}

model->submitAll();
model->setEditStrategy(QSqlTableModel::OnRowChange);

updateActions();
}

void Browser::updateActions()
{
bool enableIns = qobject_cast<QSqlTableModel *>(table->model());
bool enableDel = enableIns && table->currentIndex().isValid();

insertRowAction->setEnabled(enableIns);
deleteRowAction->setEnabled(enableDel);
}

void Browser::about()
{
QMessageBox::about(this, tr("About"), tr("The SQL Browser demonstration "
"shows how a data browser can be used to visualize the results of SQL"
"statements on a live database"));
}

**Lesiok** · 11th April 2013, 08:57

As db name You must put full path to Your db file.

**rushanbashir** · 11th April 2013, 17:34

Thank You So much :-)
Database has been connected successfully :-)

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