Better query efficiency

[Nestafaria]

I have an plsql script containing something like this:

daylist =
"01
02
...
"
hourlist =
"01
02
03
...
"
minutelist =
"00
01
...
"
for day in daylist; do
for hour in hourlist; do
for minute in minutelist; do
Select $day$hour$minute
do stuff...

I am having no problem getting this to work, but with large amounts of data it takes some time.
My question is: Is their a more efficient way to go about this??

Thanks in advance