Using ratio_to_report analytic - sql

Question

I am trying to get the percentage of rows that a set of particular value has. Best explained by example. I can do this by each column very simply using ratio-to-report function and over(), but am having issues with multiple groupings
Assume table has 2 columns:
column a column b
1000 some data
1100 some data
2000 some data
1400 some data
1500 some data
With the following query, I can get for this domain set, each one is 20% of the total rows
select columna, count(*), trunc(ratio_to_report(count(columna)) over() * 100, 2) as perc
from table
group by columna
order by perc desc;
However, what I need is for example to determine the percentage & count of the rows that contain 1000, 1400 or 2000; From looking at it, you can tell its 60%, but need a query to return that. This needs to be efficient, as the query will be running against millions of rows. Like I said before, I have this working on a single value and its percentage, but the multiple is what is throwing me.
Seems like I need to be able to put an IN clause somewhere, but the values will not be these specific values each time. I will need to get the values for the "IN" part of it from another table, if that makes sense. guess I need some kind of multiple grouping.

Answer 1

Potentially, you're looking for something like
SQL> ed
Wrote file afiedt.buf
1 with x as (
2 select 1000 a from dual
3 union all
4 select 1100 from dual
5 union all
6 select 1400 from dual
7 union all
8 select 1500 from dual
9 union all
10 select 2000 from dual
11 )
12 select (case when a in (1000,1400,1500)
13 then 1
14 else 0
15 end) bucket,
16 count(*),
17 ratio_to_report(count(*)) over ()
18 from x
19 group by (case when a in (1000,1400,1500)
20 then 1
21 else 0
22* end)
SQL> /
BUCKET COUNT(*) RATIO_TO_REPORT(COUNT(*))OVER()
---------- ---------- -------------------------------
1 3 .6
0 2 .4

Answer 2

I'm not sure I entirely understand the requirement, but do you need ratio_to_report at all? Have a look at the following, and let me know how close this is to what you want, and we can work from there!
T1 is the table containing your sample data
create table t1(a primary key) as
select 1000 as a from dual union all
select 1100 as a from dual union all
select 1400 as a from dual union all
select 1500 as a from dual union all
select 2000 as a from dual;
T2 is the lookup table you mentioned (where you get the list of IDs)
create table t2(a primary key) as
select 1000 as a from dual union all
select 1400 as a from dual union all
select 2000 as a from dual;
A left join from T1->T2 will return all rows in T1 paired with all matching rows in T2. For each A in T1 that does not exist in your set (T2), the result will be padded with NULL. We can exploit the fact that COUNT() doesn't count (hehe) nulls.
select count(t1.a) as num_rows
,count(t2.a) as in_set
,count(t2.a) / count(t1.a) as shr_in_set
from t1
left
join t2 on(t1.a = t2.a);
The result of running the query is:
NUM_ROWS IN_SET SHR_IN_SET
---------- ---------- ----------
5 3 ,6