Creating buckets or histograms with a query

Question

I know I can do what is below with a case statement defining each range. How do I make it dynamic?
I know about the width_bucket and ntile functions. I am having trouble getting them to do what I want.
I created the following table to get counts of duplicate names
create table name_dupe as
select name,count(*) mycount
from mynametable
group by name
having count(*) > 1
I now want to find out how many duplicate names fit into certian counts.
for example
How many names have between 101 and 200 duplicates, 201 and 300. 301 and 400
and so on. I may want to change the bucket ranges.
how do I do this? I think its with width_bucket and not ntile, but I can't get it to work. This iw what I tried.
select distinct mycount,dupes
from (
select mycount,width_bucket(mycount,200,300,30) dupes
from name_dupe
where dupes > 0
order by mycount
sample output:
mycount dupe
    887         31
    909         31
    993         31
   1034         31
   1341         31
   1431         31
   1490         31
   1604         31
   1664         31
   1721         31
   2106         31Edited by: Guess2 on Oct 6, 2011 11:15 AM
Edited by: Guess2 on Oct 6, 2011 11:50 AM

Answer 1

Guess2 wrote:
I know I can do what is below with a case statement defining each range. How do I make it dynamic?
I know about the width_bucket and ntile functions. I am having trouble getting them to do what I want.
I created the following table to get counts of duplicate names
create table name_dupe as
select name,count(*) mycount
from mynametable
group by name
having count(*) > 1
I now want to find out how many duplicate names fit into certian counts.
for example
How many names have between 101 and 200 duplicates, 201 and 300. 301 and 400
and so on. I may want to change the bucket ranges.
how do I do this? I think its with width_bucket and not ntile, but I can't get it to work. This iw what I tried.
select distinct mycount,dupes
from (
select mycount,width_bucket(mycount,200,300,30) dupes
from name_dupe
where dupes > 0
order by mycount
sample output:
mycount dupe
887         31
909         31
993         31
1034         31
1341         31
1431         31
1490         31
1604         31
1664         31
1721         31
2106         31Edited by: Guess2 on Oct 6, 2011 11:15 AM
Edited by: Guess2 on Oct 6, 2011 11:50 AM
width_bucket(mycount,200,300,30) According to this function you've tried to build 30-bucket histogram from 200 to 300 with step 3 (300-200)/30 all overloaded values more then 300 went to group 31.
If you want to cover your range you should use function with parameter like this:
width_bucket(mycount,200,3000,30)