This is a training task for SQL.
The slides are form Prof. Qi LIu from USTC, you can visit his website for more information.
The tasks are stored in the folder Task.
You should fork this repo, and git clone the repo to your own local machine.
Then git checkout -b $NAME to create a new branch, here $NAME is something you choose youself.
Create a folder under answer, and put your answer there, as shown by the example in answer/Gao/task_1.md.
After that done, use git add .; git commit -m "$something to say"; git push to upload, and the create a Pull Request to this repo.