How to make positions in the database?

Question

Database design

I have a plate in which the records should go in order
1 - position 1
2 - position 2
3 - position 3
4 - position 4
5 - position 5
I want, for example, to shift 1 element by 3 positions, it will be after 4 elements, the rest will move 1 forward
I would also like to be able to move the element to the end of the list
. How can this be done?

Answer 1

shift 1 element by 3 positions

UPDATE … SET line = line + 3

move element to end of list

UPDATE … SET line = ( SELECT MAX(line) + 1 … )