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Thread: What does QSqlError(-1, "", "") mean?

  1. #1
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    Default What does QSqlError(-1, "", "") mean?

    Hi again,

    I keep getting the QSqlError(-1, "", "") return from lastError() after I try to select a row from a SQLite table. I checked the query buy using it directly in the SQLite table via the FireFox plugin. The connection to the database is also okay. The code I am using to get the line I have been using over and over and it always worked as intended. I just cannot figure out what the difference is here. Does anyone know what this error message means?
    Here is the code that is not working:
    Qt Code:
    1. if(conOpen()){ // here I open the connection to the db and get an output connected, so the connection is okay
    2. QSqlQuery* query=new QSqlQuery(myDB);
    3. query->prepare("SELECT * FROM chars WHERE type='steel' AND class='V2A'");
    4. if(query->exec() && query->size() > 0){ // if I don't use the size() the next lines provides an error telling me that there is no value(1)
    5. qDebug() << query->value(1).toString();
    6. }else{
    7. qDebug() << query->lastError(); // -> here I get the error QSqlError(-1, "", "")
    8. }
    9. conClose();
    10. }else{
    11. ui->log->append("No connection");
    12. }
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  2. #2
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    Default Re: What does QSqlError(-1, "", "") mean?

    This is most likely the default constructed QSqlError instance, i.e. no error.

    Cheers,
    _

  3. #3
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    Default Re: What does QSqlError(-1, "", "") mean?

    This is "no error" because query->exec() == true but query->size() == 0. Perhaps query->size() == 0 is an error in the logic of your program but it is not a SQL error.
    P.S.
    Using construction
    Qt Code:
    1. query.exec("SELECT * FROM ....");
    2. query.value(1);
    To copy to clipboard, switch view to plain text mode 
    is bad because no database does not guarantee the order of the columns in such queries.

  4. #4
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    Default Re: What does QSqlError(-1, "", "") mean?

    Hi!

    Thanks for the hints. If I had configured my profile right I would have gotten a info that there were replies and would not have wasted the entire day...

    Your are absolutely right. QSqlError(-1, "", "") is no error. I added an query->next() and then I had all my data.

  5. #5
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    Default Re: What does QSqlError(-1, "", "") mean?

    Only some database drivers support returning the result set size. See QSqlDriver::hasFeature()

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