How to count no.of Intervals?

[#1]

Hi ,

    I have table with name,id,date, startinterval and endinterval(halfhour wise) fields.My requirement is:

i need to calculate

if(each Endinterval count id's/ecah Startinterval count if id's)>=70% then take how many intervals getting more than 70% then take count of intervals. like wise for all intervals.

I need to show this value in chart datewise how many intervals getting more than 70%.

EX:

Startinterval      Endinterval

10:30               10:30

10:30               10:30

10:30                11:00
11:00                11:00

11:30               12:00

12:00                12:30

Thanks

Ashok.

[#2]

if I understand