I can't Insert a new data to SQLITE

wenks21

I tried to insert new data to the database. here's my code:
@#include "mainwindow.h"
#include <QtSql/QSqlDatabase>
#include <QtDebug>
#include <QtGui/QApplication>
#include <QtSql>

int main(int argc, char *argv[])
{
QApplication app(argc, argv);

//MainWindow mainWindow;
//mainWindow.setOrientation(MainWindow::ScreenOrientationAuto);
//mainWindow.showExpanded();

QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
db.setDatabaseName("C:\sqlite3\sample1.db");

if(!db.open())
{
    qFatal("Failed to connect!");
}

else

qDebug("Connected.");

QSqlQuery qry;

qry.prepare("insert into sample1.db (firstname, lastname) values ('John','Dean')");
if (!qry.exec&#40;&#41;)

    qDebug() << qry.lastError();

else
  qDebug("Inserted");


db.close();
return 0;

return app.exec();

}
@

It has no errors but when I look into my sqlite using SELECT statement to see if it works, nothings happened the data that I want to add is not there.

thanks in advance!

leon.anavi

Hi,

You should create table in the database and then to insert values into the table. Test your queries with SQlite command line tool such as sqlite3.exe before adding them to the source code.

Cheers,
Leon

andre

I think your database name is invalid. Remember, a backslash is used for escaping in C++ strings... It is good practice to only use backslashes for the display of paths on platforms where a backslash is the path separator (you do that translation using QDir::toNativeSeparators). In your own code, use forward slashes only.

leon.anavi

Hi again,

I just want to post several useful links which will solve the issue:
"CREATE TABLE":http://www.sqlite.org/lang_createtable.html
Examples:
"Creating an SQLite database in Qt":http://wiki.forum.nokia.com/index.php/CS001504_-Creating_an_SQLite_database_in_Qt
"Creating a database table in Qt":http://wiki.forum.nokia.com/index.php/CS001505-Creating_a_database_table_in_Qt
"Inserting a row into a database in Qt":http://wiki.forum.nokia.com/index.php/CS001506-_Inserting_a_row_into_a_database_in_Qt

Follow the examples in the order I have posted them, merge them into a single application and you will solve the issues.

wenks21

thanks to both of you! now I modified the code. but still nothing happened.

here's the code:
@#include "mainwindow.h"
#include <QtSql/QSqlDatabase>
#include <QtDebug>
#include <QtGui/QApplication>
#include <QtSql>

int main(int argc, char *argv[])
{
QApplication app(argc, argv);

//MainWindow mainWindow;
//mainWindow.setOrientation(MainWindow::ScreenOrientationAuto);
//mainWindow.showExpanded();

QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
db.setDatabaseName("C:/sqlite3/sample1.db");

if(!db.open())
{
    qFatal("Failed to connect!");
}

else

qDebug("Connected.");

QSqlQuery qry;

qry.prepare( "CREATE TABLE IF NOT EXISTS names (id INTEGER UNIQUE PRIMARY KEY, firstname VARCHAR(30), lastname VARCHAR(30))" );
  if( !qry.exec&#40;&#41; )
    qDebug() << qry.lastError();
  else
    qDebug() << "Table created!";

qry.prepare("insert into names (id, firstname, lastname) values (1, 'John','Dean')");
if (!qry.exec&#40;&#41;)

    qDebug() << qry.lastError();

else
  qDebug("Inserted");


db.close();
return 0;

return app.exec();

}
@

is there something in the code that i have to replace?

leon.anavi

[quote author="wenks21" date="1305614955"]is there something in the code that i have to replace?[/quote]

Have you tested your SQL statements only using the command line tool? Are they OK?

Best regards,
Leon

wenks21

when i tried to test it in the command prompt in the directory of the sqlite to see if it works it said that "Error: no such table names".

andre

How far did you get? What is the output your program generated?

wenks21

It only connects to the database.

andre

[quote author="wenks21" date="1305615786"]It only connects to the database.[/quote]
So... after the "Connected." output, you get nothing else? Your code suggests that you should either get an error or an OK for both the queries you try to execute. If you get an error, please show it.

Edit:
I think you are messing up the constructors of your QSqlQuery object. Try to use the constructor that takes a QSqlDatabase argument.

wenks21

yes exactly. after the 'Connected' output nothing else happened.

how to do the constructor that you are saying? any samples?

thanks a lot!

andre

You might try the QSqlQuery documentation to learn about the different constructors for that class...

If you get no other output, you might try to set a breakpoint at the place where you last get output, and follow the program execution statement by statement by running in debug mode (F5 in Qt Creator).

wenks21

ok thanks for the info!

aureliocano

Hi wenks21,

Did you resolve your problem?
I am in the same point... :(

solareclectic

You need to open the actual file before opening the database within, like so....
@
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
QFile newdbfile(QDir::toNativeSeparators(QDir::homePath()+"/test.sqlt"));
db.setDatabaseName(newdbfile.fileName());

if (newdbfile.open(QIODevice::ReadWrite))
{
   if(!db.open())
   {
       qFatal("Failed to connect!");
   }
   else
   qDebug("Connected.");
}

@

notice, that I wrapped your db.open() with a newdbfile.open().
also, this little dance I did sure makes it easy to move around 'tween machines and platforms
@

QFile newdbfile&#40;QDir::toNativeSeparators(QDir::homePath(&#41;+"/test.sqlt"));
db.setDatabaseName(newdbfile.fileName());

@

I built and ran this code inserted into your code. It works.

lgeyer

[quote author="solareclectic" date="1309313429"]You need to open the actual file before opening the database within, like so....[/quote]

You do not need to open the file. If the code above does not work it is most likely that you

have no permission to write to the C:/sqlite3 directory
have no directory C:/sqlite3, which prevents the QSQLITE driver from creating the file (this might be the reason why opening - and thus creating - the file solves your problem)

silver47

Hi.
I tested your code and it works fine. Did you forget to add QT += sql in your .pro file?

aureliocano

Hi,

I have the same error with solareclectic code, The db is created and after 'Connected' output I don't get nothing, the table is not created.

Yes, I added QT += sql in my .pro file.

There is something I omitted because I didn't give importance and it is that I use QSQLITE2 driver instead of QSQLITE, could this be the error?

Thanks!

silver47

Qt doc:

bq. The Qt SQLite 2 plugin is offered for compatibility. Whenever possible, use the version 3 plugin instead.

dialingo

If more than one instance of the application is running the database can be locked. Do not step into this trap as I did several times.