file is encrypted or is not a database , QT - database

Question

Sorry for posting this even though there're a few posts about this , but they're not helping.
I'm using sqlite with QT , I wanted to do a simple query but it gives me this error:
file is encrypted or is not a database Unable to execute statement
Some posts' comments say that the DB may be corrupt, I used another program and created a test table from scratch and still has the same problem, this is the code:
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
db.setDatabaseName("AdmissionTestDB.sql");
db.open();
if(db.isOpen())
{
QSqlQuery q = db.exec("SELECT * FROM USERS");
if(!q.lastError().isValid())
{
qDebug()<<"works!";
while(q.next())
{
qDebug()<<q.value(8).toString();
}
}
else
qDebug()<<"---db failed to open! , error: "<<q.lastError().text();
db.close();
return true;
}
qDebug()<<"db failed to open! , error: "<<db.lastError().text();
return false;
More Information hopefully it would help solving this:
1- I'm using SQLITE 3
2- The problem happens when I use QSqlQuery q = db.exec("SELECT * FROM USERS"); so the DB actually opens!
3- I used two GUI programs to create the DB one of them is the latest version of SQLiteStudio which is version 3.0.4