QSqlQuery causing ODBC Function sequence error

Question

It seems due to ODBC functions being called out out of order. But since I am using QSql that wraps ODBC, it is hard for me to track down the function.

• I was able to connect to the SQL server database
• I tested a very simply query and still got the error. I don't think it's due to column binding.
• I was able to run the query with SQL server, so I think the SQL query is ok.

1. The tools I am using:

VS c++ 2017, CMake, Qt 5.09.2, SQL server 2017

2. Below are the error messages:

QODBCResult::exec: Unable to execute statement: "[Microsoft][ODBC Driver Manager] Function sequence error"
QSqlError("0", "QODBC3: Unable to execute statement", "[Microsoft][ODBC Driver Manager] Function sequence error")

3. Test coding:

   This coding generate the error message above.

   int main()
   {
        QSqlDatabase GUIInpDB = QSqlDatabase::addDatabase("QODBC", "MainSQLDB");
        GUIInpDB.setConnectOptions();
        QString inpSqlServer = "DESKTOP-085AEA8\\SQLEXPRESS";
        QString dbName = "test";
        QString connString = QString("Driver={ODBC Driver 13 for SQL Server};Server=%1;DATABASE=%2;Trusted_Connection=Yes;")
            .arg(inpSqlServer).arg(dbName); //the argument replace the %1 and %2
        GUIInpDB.setDatabaseName(connString);
        QSqlDatabase db = QSqlDatabase::database("MainSQLDB");
   
        if (!db.open())
        {
            qDebug() << "Connection for db not working";
            return 1;
        }
        QSqlQuery query("SELECT * FROM TBL.tbl_test", db);  
        if (!query.exec())
            qDebug() << query.lastError();
   
        int num_of_rows = query.size();
   
        getchar();
        return 0;
   }
   

Answer 1

From ODBC function sequence error:

The documentation for the QSqlQuery constructor says "If query is not an empty string, it will be executed.", which means that when you call exec() you are executing it twice.

QSqlQuery::QSqlQuery(const QString &query = QString(), const QSqlDatabase &db = QSqlDatabase()).