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Thread: No query Unable to fetch row when ERROR , when trying to do a simple query

  1. #1
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    Default No query Unable to fetch row when ERROR , when trying to do a simple query

    I have a sqlite 3 database where I have some fake data just for testing, but it seems that every time I try to do a simple query it gives me the error that I mentioned in the title.

    here's the code:

    Qt Code:
    1. QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
    2. db.setDatabaseName("adtDB.sql");
    3. db.open();
    4. if(db.isOpen())
    5. {
    6. QSqlQuery q = db.exec("SELECT * FROM adt");
    7. if(q.exec())
    8. {
    9. qDebug()<<"works!";
    10. while(q.next())
    11. {
    12. qDebug()<<q.value(8).toString();
    13. }
    14. }
    15. qDebug()<<"---db failed to open! , error: "<<q.lastError().text();
    16. db.close();
    17. return true;
    18. }
    19. qDebug()<<"db failed to open! , error: "<<db.lastError().text();
    20. return false;
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    The database opens fine but this is the error that I get including the debug statement:
    ---db failed to open! , error: "No query Unable to fetch row"

    the red text is the error the rest is in the debug statement that I included.

  2. #2
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    Default Re: No query Unable to fetch row when ERROR , when trying to do a simple query

    You are doing 2 times exec(). Code should looks like :
    Qt Code:
    1. QSqlQuery q = db.exec("SELECT * FROM adt");
    2. if(!q.lastError().isValid())
    3. {
    4. qDebug()<<"works!";
    5. while(q.next())
    6. {
    7. qDebug()<<q.value(8).toString();
    8. }
    9. }
    10. else
    11. {
    12. qDebug()<<"---db failed to open! , error: "<<q.lastError().text();
    13. }
    14. db.close();
    15. return true;
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  3. #3
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    Default Re: No query Unable to fetch row when ERROR , when trying to do a simple query

    Quote Originally Posted by Lesiok View Post
    You are doing 2 times exec(). Code should looks like :
    Qt Code:
    1. QSqlQuery q = db.exec("SELECT * FROM adt");
    2. if(!q.lastError().isValid())
    3. {
    4. qDebug()<<"works!";
    5. while(q.next())
    6. {
    7. qDebug()<<q.value(8).toString();
    8. }
    9. }
    10. else
    11. {
    12. qDebug()<<"---db failed to open! , error: "<<q.lastError().text();
    13. }
    14. db.close();
    15. return true;
    To copy to clipboard, switch view to plain text mode 
    Thanks for your answer but this gives me another error:

    file is encrypted or is not a database Unable to execute statement

    new code:

    Qt Code:
    1. QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
    2. db.setDatabaseName("adtDB.sql");
    3. db.open();
    4. if(db.isOpen())
    5. {
    6. QSqlQuery q = db.exec("SELECT * FROM adt");
    7. if(!q.lastError().isValid())
    8. {
    9. qDebug()<<"works!";
    10. while(q.next())
    11. {
    12. qDebug()<<q.value(8).toString();
    13. }
    14. }
    15. qDebug()<<"---db failed to open! , error: "<<q.lastError().text();
    16. db.close();
    17. return true;
    18. }
    19. qDebug()<<"db failed to open! , error: "<<db.lastError().text();
    20. return false;
    To copy to clipboard, switch view to plain text mode 

  4. #4
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    Default Re: No query Unable to fetch row when ERROR , when trying to do a simple query

    Sorry for commenting so the post will go to the top, but this problem is pretty annoying and I really need a fix since I need to finish this in two days to submit it.

  5. #5
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    Default Re: No query Unable to fetch row when ERROR , when trying to do a simple query

    From which line is this error : 15 or 19 ? Description of error is clear. The database is encrypted or damaged.

  6. #6
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    Default Re: No query Unable to fetch row when ERROR , when trying to do a simple query

    It's from line 15

  7. #7
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    Default Re: No query Unable to fetch row when ERROR , when trying to do a simple query

    Line 15 is pointless. Compare my code and Your.

  8. #8
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    Default Re: No query Unable to fetch row when ERROR , when trying to do a simple query

    Can you access this database using the sqlite3 command line program and execute your query successfully? If not, then your Qt program certainly won't be able to either.

    Since you are specifying a relative file name for your database, you may be creating an empty file inadvertently by opening your database in a different working directory than you think.

    Try hard coding the fully qualified file path and see if that works and/or search your drive for your file name and see if you have another file created somewhere you did not intend, etc.
    Last edited by jefftee; 16th April 2015 at 17:28.

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