How to get the correct QSqlError?

[deleted385]

@jsulm, it didn't catch error, it opened an invalid file ie, the MakeFile as database.

[jsulm]

@Emon-Haque Doesn't change the fact that this part of your code is logically wrong.
Qith SQLite you will not get an error as far as I know if the file is not there. Not sure what happens if the file exists but is not a database file.

[JonB]

@Emon-Haque said in How to get the correct QSqlError?:

it didn't catch error

Evidently SQLite does not consider/report an error at the time of opening a file, whatever it contains. Only later when it tries to perform some SQL operation on it does it complain.

[deleted385]

@jsulm, yes that's obviously wrong and thanks for reminding me about that. Before posting topic, I try to make it compact. If I'd done it in correct way, I'd have to add some extra lines, braces, etc.

[deleted385]

@JonB, when I call model->fetchMore, where model is a QSqlQueryModel, with an invalid file, I get file is not a database Unable to execute statement if I give it some string, If I give it an empty string, it says No Error.

With QSqlQuery query("SELECT * FROM sqlite_master", db); in ObjectsView, I got connection error and a message No query Unable to fetch row. Can I get the same message I got with QSqlQueryModel when it's an invalid file and I gave it some string?

[JonB]

@Emon-Haque
Well, to an extent you get whatever you get as error messages, I know no more than that!

However:

   model->setQuery(query, db);
   while (model->canFetchMore()) model->fetchMore();

You do not check the result from setQuery() before you proceed to canFetchMore(). Per void QSqlQueryModel::setQuery(const QString &query, const QSqlDatabase &db = QSqlDatabase()):

lastError() can be used to retrieve verbose information if there was an error setting the query.

So you should check model->lastError() immediately after the setQuery()?

[deleted385]

@JonB, will try that after a break and, hopefully, will let you know what happens.

[deleted385]

@JonB, Here's what it does:

First, I gave it an invalid database and these

QSqlQuery query("SELECT * FROM sqlite_master", db);
if(query.exec()) ...
else emit logMessage(query.lastError());

gave me 08:14:41 PM : Connection error : No query Unable to fetch row, the error message is incorrect. There was query BUT the database file is invalid. Second, I clicked the play button and in the box there was no text and these

model->setQuery(query, db);
emit logMessage(model->lastError());
while (model->canFetchMore()) model->fetchMore();

gave me 08:14:48 PM : No error : , it's also incorrect. Both the database is invalid and there was no query. Third, I gave SELECT as the query and it gave me 08:14:56 PM : Statement error : incomplete input Unable to execute statement. In this case it didn't say anything about the validity of database.

EDIT
After a while I gave it SELECT * FROM x, with that invalid Makefile as database, it gave me 09:55:22 PM : Statement error : file is not a database Unable to execute statement.

So you see the variations in QSqlError. In all of those cases I should get a single message like SQLite error 26: 'file is not a database'

[JonB]

@Emon-Haque
All I can say is mostly/frequently/probably those errors come from SQLite, or maybe the SQLite driver, not Qt.

[deleted385]

These errors also vary depending on which object I'm using (QSqlQueryModel or QSqlQuery ) and with a valid database. Here's the error I got with QSqlQueryModel:

To code is:

else{
    QSqlQueryModel sqlQuery;
    bool gotError = false;
    db.transaction();
    for (int i = 0; i < statements.size(); i++) {
        auto trimmed = statements[i].trimmed();
        if(trimmed.startsWith("--")) continue;
        sqlQuery.setQuery(trimmed);
        if(sqlQuery.query().isSelect()){
            emit widget->logMessage("e,SELECT isn't allowed while executing multiple statements");
            gotError = true;
            break;
        }
        else if(sqlQuery.query().lastError().type() != QSqlError::NoError){
            emit widget->logMessage("e," + sqlQuery.query().lastError().text());
            gotError = true;
            break;
        }
    }
    ...
}

so it's correct, NewTable exists. If I replace those code with these:

else{
    bool gotError = false;
    db.transaction();
    for (int i = 0; i < statements.size(); i++) {
        auto trimmed = statements[i].trimmed();
        if(trimmed.startsWith("--")) continue;
        sqlQuery.clear();
        sqlQuery.prepare(trimmed);
        sqlQuery.exec();
        if(sqlQuery.isSelect()){
            emit widget->logMessage("e,SELECT isn't allowed while executing multiple statements");
            gotError = true;
            break;
        }
        else if(sqlQuery.lastError().type() != QSqlError::NoError){
            emit widget->logMessage("e," + sqlQuery.lastError().text());
            gotError = true;
            break;
        }
    }
    ...
}

where sqlQuery is a global QSqlQuery, I get this error:

that's a misleading error I got! Am I doing something wrong or it's an issue with SQLite?

EDIT
Looks like QSqlQuery doesn't need to be executed to get error. I've to check error immediately after sqlQuery.prepare(trimmed); and if there's no error then I should call sqlQuery.exec(). In a nutshell, Qt executes the query, and figures out the error, before I call exec.