Totally Waste of time. They don't know what kinds of people they want. They asked you to finish 2 simple SQL questions in two days and then ask skill-set files and samples and then ask other questions in email. The HR appointment they scheduled with you is only a 15-minute call, but apparently, they're too impatient to have a brief conversation, so they'll bombard you with a plethora of questions via email instead. Then you can expect they change the appointment time directly on your calender without any notice. The first time has such unprofessional and unrespectful HR interview experience.