Maintaining a Relative Order of Flex Tasks in a SQL DB

I have a task scheduling app that allows people to create 2 types of tasks...

•Strict- tasks with a set start time and duration •Flex- tasks that have a duration, but no specific start time

Its also important to understand how flex tasks operate- Flex tasks will continuously reschedule themselves throughout your day in the nearest time you have open...so for example if the only task on your schedule today is a flex task like "Go workout - duration:60mins" and you open the app at 4pm it will have "Go workout" scheduled from 4-5pm for you , if you dont click the checkbox indicating you completed the task and open the app again at 5PM "Go workout will be rescheduled to 5-6pm so that the stuff you are meaning to get done is constantly in your face and trying to fit itself into the gaps of your life.

When a user views their schedule here are the steps I go through: •Grab a array of all strict tasks •Grab a array of all flex tasks •Loop through each strict task and figure out how big of a time gap there is between the task currently being looped's end time and the next tasks start time. •if a gap exists loop through the flex tasks and see if any of them will fit in the time gap in question. if a flex task is small enough to fit in the time gap add it to the strictTasksArray between the task being currently looped and the next task.

This works great as long as there is no need for any kind of ordering when it comes to flex tasks, but now we have added the ability for users to drag and drop flex tasks into a specific relative order aka if I have Task A,B,C,D and I drag Task D & B to the front so that its now D,B,A,C it needs to save that ordering so that if you close and reopen the app the app will still remember to try to fit task D in , followed by B, A & C .....but im having big trouble thinking of a efficient way to do considering the ordering is relative and not strict...any ideas how to save relative ordering in a SQLIte DB without having to update every tasks's DB record every time a user drag/drops a task and changes the relative ordering?