Need Help Creating Query

I am working with employee schedules. Each schedule is comprised of
segments (shift, lunch, break, training, etc.) that have rankings.
Each record has the employee id, the date the shift starts, the start
and end time of each segment, the duration,the segment type and its
rank. The start and end times of the schedules can overlap, but the
segment that has the higher rank takes precedence.

As a simple example, an employee working 8a-5p will have two records.
The shift segment from 8a-5p and a lunch segment from 12p-1p. The
lunch ranks higher so, even though the shift goes from 8a-5p, from
12p-1p, the lunch takes precedence.

What I'm trying to do is build a query that will collapse the segments.
So given the example above, I will now have three records: shift
8a-12p, lunch 12p-1p, shift 1p-5p.

I have been racking my brain but I just can't figure it out.
Ultimately, a programmer in my office will display this in a bar chart
format with each segment type having its own color. I'm trying to do as
much of the work in SQL so he doesn't have to calculate this stuff in
the code.

Any help would be appreciated.

Thanks.
Angela