如何构造子查询/ CTE来替换嵌套的聚合函数？

Question

I am trying to find out what percent of the 'amt' values belongs to each of the 'percent' buckets.

Example Data:

amt | pct
5   | .5
10  | .6
15  |  1
20  | .8

Desired Results:

pctAMT | PCTrange
.3     | <65
.4     | 75-84
.3     | 100+

I've tried using a nested aggregate function, and also trying to use the total as a single value. However, I'm running into errors. I think I have to re-structure the query as a CTE or subquery but I'm not sure how.

SELECT SUM(amt)/(SUM(amt) OVER()) AS pctAMT,
CASE WHEN percent < .65 then '  <65'
            WHEN .65 <= percent AND percent <.75  then '65-74'
            WHEN .75 <= percent AND percent <.85  then '75-84'
            WHEN .85 <= percent AND percent <.95  then '85-94'
            WHEN .95 <= percent AND percent <1.00 then '95-99'
            WHEN .100 <= percent  then ' 100+'
        END PCTrange
FROM table
WHERE date = TO_DATE('2016-04-01','YYYY-MM-DD')
GROUP BY PCTrange
ORDER BY PCTrange;

ERROR [HY000] ERROR:  Attribute LN_HIST.LN_FNCL_RPTG_UPB must be GROUPed or used in an aggregate function

Answer 1

I would expect something like this:

SELECT (CASE WHEN percent < 0.65 then '  <65'
             WHEN percent < 0.75 then '65-74'
             WHEN percent < 0.85 then '75-84'
             WHEN percent < 0.95 then '85-94'
             WHEN percent < 1.00 then '95-99'
             ELSE ' 100+'
        END) as PCTrange,
       SUM(amt)/ SUM(SUM(amt)) OVER () AS pctAMT
FROM table
WHERE date = '2016-04-01'
GROUP BY PCTrange
ORDER BY PCTrange;

The important change is SUM(SUM()) -- adding up the sums for division.

I also simplified the CASE expression. The clauses are evaluated in order, so you can take advantage of that. The date comparison is also simpler.