QSqlDatabasePrivate::removeDatabase: connection '05465461654654' is still in use, all queries will cease to work

[static] void QSqlDatabase::removeDatabase(const QString &connectionName)
Removes the database connection connectionName from the list of database connections.
Warning: There should be no open queries on the database connection when this function is called, otherwise a resource leak will occur.
Example:

  // WRONG
  QSqlDatabase db = QSqlDatabase::database("sales");
  QSqlQuery query("SELECT NAME, DOB FROM EMPLOYEES", db);
  QSqlDatabase::removeDatabase("sales"); // will output a warning

  // "db" is now a dangling invalid database connection,
  // "query" contains an invalid result set

The correct way to do it:

  {
      QSqlDatabase db = QSqlDatabase::database("sales");
      QSqlQuery query("SELECT NAME, DOB FROM EMPLOYEES", db);
  }
  // Both "db" and "query" are destroyed because they are out of scope
  QSqlDatabase::removeDatabase("sales"); // correct

To remove the default connection, which may have been created with a call to addDatabase() not specifying a connection name, you can retrieve the default connection name by calling connectionName() on the database returned by database(). Note that if a default database hasn't been created an invalid database will be returned.
Note: This function is thread-safe.

{
 QSqlDatabase db = QSqlDatabase::database(“sales”);
 QSqlQuery query(“SELECT NAME, DOB FROM EMPLOYEES”, db);
 }
 // Both “db” and “query” are destroyed because they are out of scope
 QSqlDatabase::removeDatabase(“sales”);