From the looks of it, you have to re-create the models when you change these settings.

@SGaist I did it this way for reading return params:

Query.nextResult(); // after reading table values //Get Return Parameter for (int i=0; i<CountReturnParam; i++) { qDebug() << QString("Returnparam %1 = %2") .arg(i).arg(Query.boundValue(i).toString()); }

Hi,

What version of Qt are you using ?

You should print the error you get if exec fails. That will give you clues as to what is happening.

On a side note, QString already provides easy to use arguments handling so you don't have to use snprintf.

@jsulm Thanks a lot!
Sorry for my miss on the link.
I will try it.

@koahnig
Well the "MySQL server has gone away" msg also seems slightly "wooden" so it fits perfectly :)

@_compiler

Ok, i see, its a helper class.

Well you need to open a db then.

You dont need to do it in QueryBuilder.

If you open a db in main , QSqlQuery
will use this DB. You dont need pointer or reference.
Its handled internally.

Glad you found out and thanks for sharing !

Since you have it working now, please mark the thread as solved using the "Topic Tools" button so that other forum users may know a solution has been found :)

To add to @the_ , if you only have one database connection and don't give it a name, it becomes the default connection and you don't need to call QSqlDatabase::database each time you make a query.

@panosk

and to be honest I had already started work on this

You already have that in QSqlDatabase, you only need to keep track of the connections' names.

Good luck!

@Ottaviane said:

Crea un link alla con il comando ln :
ln -s /usr/lib64/libmysqlclient.so.18.0.0 /usr/lib64/libmysqlclient_r.so

Hi, I got the libqsqlodbc.so plugin to load successfully, I think it was last year with Qt 5.2 or 5.3, but I remember I had same kind of difficulties because the libqsqlodbc.so plugin is depending on libodbc.so being in the correct place. You could check with
ldd libqsqlodbc.so
to see what .so files are missing..

@Gualtix Hi and welcome to devnet, you are not following the current documented procedure.

Done :)

I'm using this code on the server. By blocking I simply meant that if one client requested something that took long to process it shouldn't block the other clients. I may upload a working sample of this code to github later.

for anyone else who wants to know how to do it, this is what I did.

add this to one of you header files

#include <sqlite3.h> #include <QSqlDriver>

add this to your .pro file

INCLUDEPATH += $$[QT_INSTALL_PREFIX]/src/3rdparty/sqlite SOURCES += $$[QT_INSTALL_PREFIX]/src/3rdparty/sqlite/sqlite3.c

and in your MainWindow.cpp file add

sqlite3_temp_directory = path-to-dir;

IMPORTANT
if you used homebrew to install qt5, they do NOT install the sources, you will have to downloaded the sources from the qt.io website extract and copy the qtbase/src folder to wherever $$[QT_INSTALL_PREFIX] is.

also this does compile, but I haven't tested to see if the files actually get stored where I set, so...

Adapted from the documentation example: model->setFilter("should_alarm=1");

Hi,

@sarai Yes QFile does: it's the file name. QSqlDatabase allows you to handle one or more database connections through multiple possible drivers at the same time in a easy to use fashion. The design avoids you to have to create a QSqlDatabase instance and setting it up again and again in each class/function of your application where you would like to run a query. That also means that you don't have to put your credentials everywhere in your application. That way, you can easily get the connection you need in a multi database setup.

Are you using a Linux machine? Please, to have better help you should describe the scenario.

I'm not familiar with Oracle, but this looks close enough to Postgresql that I'll show how I would do it in PG/SQL in hopes that it will be useful.

I would create the function in the database

CREATE OR REPLACE FUNCTIOM test_fucntion(_name TEXT)
RETURNS BIGINT AS $BODY$
DECLARE
_rv BIGINT
BEGIN
INSERT INTO test_table(name)
VALUES(_name) RETURNING id into _rv;
RETURN _rv;
END;
$BODY$
LANGUAGE plpgsql;

After adding that function to the database you can simply execute the query
SELECT * from test_function("name");
to get your ID.

As I said, this is Postgres code, but I'm pretty sure the Postgres authors imitated Oracle to some extent.

Mike

You're welcome !

Since everything is working now, please mark the thread as solved so other forum users may know a solution has been found :)

At the end it was a typo. I was trying to insert a value into a column called Localización by using:

guardar_s.prepare("INSERT INTO Solicitudes_Trabajo (Localizacion)

The problem is in the accent mark.

So if anyone gets this error, watch out the typos.

Thanks @clochydd !

Al final guardando cada valor de las dos bases de datos en QStrings funcionaba:

QString _Telefono = seleccionar2.value(8).toByteArray().constData(); QString _Tecnico_Asignado = seleccionar2.value(0).toByteArray().constData(); QString _Estado_Solicitud = seleccionar2.value(7).toByteArray().constData();

Así podía usar este código sin problema:

QSqlQuery guardar_s; guardar_s.prepare("INSERT INTO Solicitudes_Trabajo (N_Solicitud, Fecha_Emision, Unidad_Hospitalaria," "Codigo_Equipo, Equipo, Marca)" "VALUES (:N_Solicitud, :Fecha_Emision, :Unidad_Hospitalaria, :Codigo_Equipo, :Equipo," ":Marca)"); guardar_s.bindValue(":N_Solicitud", _N_Solicitud); guardar_s.bindValue(":Fecha_Emision", _Fecha_Emision); guardar_s.bindValue(":Unidad_Hospitalaria", _Unidad_Hospitalaria); guardar_s.bindValue(":Codigo_Equipo", _Codigo_Equipo); guardar_s.bindValue(":Equipo", _Equipo); guardar_s.bindValue(":Marca", _Marca);

Insertaba los valores de las dos bases de datos en la base Empresa, pero si usaba este otro con más valores no funcionaba:

QSqlQuery guardar_s; guardar_s.prepare("INSERT INTO Solicitudes_Trabajo (N_Solicitud, Fecha_Emision, Unidad_Hospitalaria, Codigo_Equipo," "Equipo, Marca, Modelo, N_Serie, Localizacion, Unidad_Tecnica, Peticionario, Telefono, " "Descripcion_Solicitud, Tecnico_Asignado, Tipo_Solicitud, Estado_Solicitud) " "VALUES (:N_Solicitud, :Fecha_Emision, :Unidad_Hospitalaria, :Codigo_Equipo, :Equipo, :Marca, :Modelo," ":N_Serie, :Localizacion, :Unidad_Tecnica, :Peticionario, :Telefono, :Descripcion_Solicitud," ":Tecnico_Asignado, :Tipo_Solicitud, :Estado_Solicitud)"); guardar_s.bindValue(":N_Solicitud", _N_Solicitud); guardar_s.bindValue(":Fecha_Emision", _Fecha_Emision); guardar_s.bindValue(":Unidad_Hospitalaria",_Unidad_Hospitalaria); guardar_s.bindValue(":Codigo_Equipo", _Codigo_Equipo); guardar_s.bindValue(":Equipo", _Equipo); guardar_s.bindValue(":Marca", _Marca); guardar_s.bindValue(":Modelo", _Modelo); guardar_s.bindValue(":N_Serie", _N_Serie); guardar_s.bindValue(":Localizacion", _Localizacion); guardar_s.bindValue(":Unidad_Tecnica", _Unidad_Tecnica); guardar_s.bindValue(":Peticionario", _Peticionario); guardar_s.bindValue(":Telefono", _Telefono); guardar_s.bindValue(":Descripcion_Solicitud", _Descripcion_Solicitud); guardar_s.bindValue(":Tecnico_Asignado", _Tecnico_Asignado); guardar_s.bindValue(":Tipo_Solicitud", "a"); guardar_s.bindValue(":Estado_Solicitud", _Estado_Solicitud);

Me daba el error: 12.ERROR: QSqlError("", "Parameter count mismatch", "").

Pensaba que quizás eran demasiados valores para Qt Creator. Pero al final, después de muchas pruebas me dí cuenta que estaba intentando insertar un valor en la columna existente Localización con un INSERT INTO Solicitudes_Trabajo (Localizacion).
Lo explico por si a alguien más le sale ese mismo error que pruebe a revisar todos los campos y columnas en busca de algún pequeño fallo en alguna letra o alguna tilde.

Solved.
I tried a lot of things to solve the problem. Some of them included calling next before accessing the result as @SGaist said, but it continued saying:

QSqlQuery::value: not positioned on a valid record

At last I created a new project with a new database and it worked properly with this code:

hospital=QSqlDatabase::addDatabase("QSQLITE"); hospital.setDatabaseName("C:/Sqlite3/Hospital.sqlite"); if(hospital.open()){ qDebug()<<"4.Se ha conectado a la base de datos Hospital"; }else{ qDebug()<<"4.ERROR. No se ha conectado a la base de datos Hospital"; } QSqlQuery mostrar; mostrar.prepare("SELECT*FROM Partes WHERE N_Parte=:ID"); mostrar.bindValue(":ID",ui->lineEditN_Parte->text()); if(mostrar.exec()) { qDebug()<<"5.Los datos del parte se han mostrado correctamente"; }else{ qDebug()<<"5.ERROR. Los datos del parte no se han mostrado correctamente"; qDebug()<<"5.ERROR:"<<mostrar.lastError(); } mostrar.next(); ui->tableWidget->setRowCount(15); QStringList Campos; Campos<<"Fecha de Emisión"<<"Unidad Hospitalaria"; ui->tableWidget->setVerticalHeaderLabels(Campos); ui->tableWidget->insertColumn(0); ui->tableWidget->setColumnCount(1); ui->tableWidget->setItem(0, 0, new QTableWidgetItem(mostrar.value(1).toByteArray().constData())); ui->tableWidget->setItem(2, 0, new QTableWidgetItem(mostrar.value(2).toByteArray().constData()));

So I guess the problem was in the database, maybe in the columns, maybe in the rows, maybe in the values or maybe in the name of each of them.

The important thing is that the code I post in this reply works perfectly, so if anyone has a similar problem I hope it helps.

Thank you very much!

Resuelto.
Intenté muchas cosas para solucionar el problem, algunas incluian la utilización de next() que me faltaba en el código de mi respuesta anterior pero continuaba saliendo el error:

QSqlQuery::value: not positioned on a valid record

Al final creé un nuevo proyecto con una base de atos nuevas y funciona correctamente con este código:

hospital=QSqlDatabase::addDatabase("QSQLITE"); hospital.setDatabaseName("C:/Sqlite3/Hospital.sqlite"); if(hospital.open()){ qDebug()<<"4.Se ha conectado a la base de datos Hospital"; }else{ qDebug()<<"4.ERROR. No se ha conectado a la base de datos Hospital"; } QSqlQuery mostrar; mostrar.prepare("SELECT*FROM Partes WHERE N_Parte=:ID"); mostrar.bindValue(":ID",ui->lineEditN_Parte->text()); if(mostrar.exec()) { qDebug()<<"5.Los datos del parte se han mostrado correctamente"; }else{ qDebug()<<"5.ERROR. Los datos del parte no se han mostrado correctamente"; qDebug()<<"5.ERROR:"<<mostrar.lastError(); } mostrar.next(); ui->tableWidget->setRowCount(15); QStringList Campos; Campos<<"Fecha de Emisión"<<"Unidad Hospitalaria"; ui->tableWidget->setVerticalHeaderLabels(Campos); ui->tableWidget->insertColumn(0); ui->tableWidget->setColumnCount(1); ui->tableWidget->setItem(0, 0, new QTableWidgetItem(mostrar.value(1).toByteArray().constData())); ui->tableWidget->setItem(2, 0, new QTableWidgetItem(mostrar.value(2).toByteArray().constData()));

Así que supongo que el problema estaba en la base de datos anterior, quizás en las columnas, quizás en las filas, quizás en los valores o quizás en el nombre de cada uno de estos elementos.
Lo importante es que el código que adjunto en esta respuesta funciona correctamente, de modo que si alguien tiene un problema parecido espero que esto le ayude.

Muchas gracias!

Note on https://dev.mysql.com/doc/refman/5.7/en/libmysqld.html says: “The libmysqld embedded server library is deprecated as of MySQL 5.7.17 and will be removed in MySQL 8.0.“

@ChrisW67 Thank you. I kind of understand what you mean, but recently I tried a solution that appears to work.
I have a class named mainWidget, in which the remaining widgets are instantiated. I simply retrieve the db connection name, store it in a variable and then whenever I switch widgets and need to re-open the database, I close said connection and addDatabase again. I am guessing this is not optimal, but it allows me to move on with the SQLite databases.

@danks_
That is good to hear !
Could also been some kind of setup problem with 5_5 but yeah it does
seems like a bug.

I will try with 5_5 and see it it fails for me too.

update:
Tested win pure 5_5 install
It worked by copying the DLLs ! ?
Even worked with no sub sqldrivers folder ...!
(in the release folder)

But when moved out of the virtual machines
it did want the sqldrivers folder to work.

So the current version of 5.5 via the online installer does seems to work in regards to sql.?!

Hi,

No black magic here, I'd say you added the sql module to your pro file but didn't run qmake before building.

Instead of ShellExecute, you can also use QProcess in Qt programs

Why you don't want use QProcess???

@simow thanks for the answer.