database open returns false

[ahmetturan]

I create a QSqlDatabase object an then I open it.

QSqlDatabase db;
db=QSqlDatabase::addDatabase("qwe.db");
db.open();

QSqlDatabase db;
db=QSqlDatabase::addDatabase("qwe.db");
db.open();

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after that isOpen() and isValid() return true.

After that when I want to connect database I wote this:

if(!db.isOpen()) -->returns false. but I never close db until app closing
{
    db.open(); -->it returns false
}

if(!db.isOpen()) -->returns false. but I never close db until app closing
{
    db.open(); -->it returns false
}

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after that isOpen() and isValid() return false;
But my queries work and I can get data from database.

What is wrong here?