SQL Query to use a Case Statement within and Aggregate Function - sql

Question

I have a query below that I need to get a count where Incident Records = 0. The first level is a summary of the records it grabs to calculate totals. I tried using COUNT(INCIDENTS!='0') but it apparently is not working though it does not error out. How would I get this count? This is in Snowflake if that is a factor. The case statement: CASE WHEN SUM(INCIDENTS) = '0' THEN '0' ELSE COUNT(INCIDENTS!='0') END AS INCIDENTS Works but the 2nd line which references those Incidents seems to only give a count but not the result of the Case Statement before it:
SELECT DRIVER_NAME, DRIVER_ID, CSC, SUM(DISTINCT(OBSERVATIONS)) AS OBSERVATIONS, --SUM(DISTINCT(INCIDENTS)) AS INCIDENTS_SUM_DISTINCT,
--COUNT(INCIDENTS) AS INCIDENTS,
COUNT(INCIDENTS!='0'),
CASE WHEN SUM(INCIDENTS) = '0' THEN '0' ELSE COUNT(INCIDENTS!='0') END AS INCIDENTS,
(COUNT(INCIDENTS!='0') / SUM(DISTINCT(OBSERVATIONS))) * 100 AS FREQUENCY_PERCENT,
1 AS GOAL, (SUM(SIX_TEN_MPH) / SUM(DISTINCT(OBSERVATIONS))) * 100 AS SIX_TEN_PERCENT,
(SUM(ELEVEN_FIFTEEN_MPH) / SUM(DISTINCT(OBSERVATIONS))) * 100 AS ELEVEN_FIFTEEN_PERCENT,
(SUM(SIXTEEN_PLUS_MPH) / SUM(DISTINCT(OBSERVATIONS))) * 100 AS SIXTEEN_PLUS_PERCENT
--SPEED_LIMIT, SPEED, DIFFERENCE, REPORT_DATE, TIME,
FROM
(
SELECT A.DRIVER_NAME AS DRIVER_NAME, A.DRIVER_ID AS DRIVER_ID, C.TRC_TERMINAL AS CSC, A.OBSERVATIONS AS OBSERVATIONS,
A.INCIDENTS AS INCIDENTS, B.SPEED_LIMIT AS SPEED_LIMIT, B.SPEED AS SPEED, B.DIFFERENCE AS DIFFERENCE,
A.REPORT_DATE AS REPORT_DATE, B.TIME AS TIME,
CASE WHEN DIFFERENCE >= 6 AND DIFFERENCE <= 10 THEN '1' WHEN DIFFERENCE IS NULL THEN '0' ELSE '0' END AS SIX_TEN_MPH,
CASE WHEN DIFFERENCE > 10 AND DIFFERENCE <= 15 THEN '1' WHEN DIFFERENCE IS NULL THEN '0' ELSE '0' END AS ELEVEN_FIFTEEN_MPH,
CASE WHEN DIFFERENCE > 15 THEN '1' WHEN DIFFERENCE IS NULL THEN '0' ELSE '0' END AS SIXTEEN_PLUS_MPH
FROM "PROD"."PUBLIC"."SG_DRIVER_TREND" A
LEFT JOIN "PROD"."PUBLIC"."SG_DRIVER_INCIDENTS" B
ON A.DRIVER_ID = B.DRIVER_ID
LEFT JOIN "PROD"."PUBLIC"."TMW_TRACTORPROFILE" C
ON B.Vehicle = C.TRC_NUMBER
WHERE A.DRIVER_ID != ''
AND A.REPORT_DATE BETWEEN '2022-07-01' AND '2022-07-31'
AND B.TIME BETWEEN '2022-07-01' AND '2022-07-31'
AND SUBSTRING(B.TIME, 0, 10) <= A.REPORT_DATE -- Less than or equal to report date
AND SUBSTRING(B.TIME, 0, 10) > SUBSTRING(DATEADD(week,-1, A.REPORT_DATE), 0, 10) -- Greater than 1 week ago
UNION
--SELECT A.DRIVER_NAME AS DRIVER_NAME, A.DRIVER_ID AS DRIVER_ID, C.TRC_TERMINAL AS CSC, A.OBSERVATIONS AS OBSERVATIONS,
-- A.INCIDENTS AS INCIDENTS, B.SPEED_LIMIT AS SPEED_LIMIT, B.SPEED AS SPEED, B.DIFFERENCE AS DIFFERENCE,
-- A.REPORT_DATE AS REPORT_DATE, B.TIME AS TIME,
SELECT DISTINCT(A.DRIVER_NAME) AS DRIVER_NAME, A.DRIVER_ID AS DRIVER_ID,
C.TRC_TERMINAL AS CSC,
--'UPT' AS CSC,
A.OBSERVATIONS AS OBSERVATIONS,
'0' AS INCIDENTS, '0' AS SPEED_LIMIT, '0' AS SPEED, '0' AS DIFFERENCE,
A.REPORT_DATE AS REPORT_DATE, '' AS TIME,
'0' AS SIX_TEN_MPH,
'0' AS ELEVEN_FIFTEEN_MPH,
'0' AS SIXTEEN_PLUS_MPH
FROM "PROD"."PUBLIC"."SG_DRIVER_TREND" A
LEFT JOIN "PROD"."PUBLIC"."SG_DRIVER_INCIDENTS" B
ON A.DRIVER_ID = B.DRIVER_ID
-- AND SUBSTRING(B.TIME, 0, 10) <= A.REPORT_DATE -- Less than or equal to report date
-- AND SUBSTRING(B.TIME, 0, 10) > SUBSTRING(DATEADD(week,-1, A.REPORT_DATE), 0, 10) -- Greater than 1 week ago
INNER JOIN "PROD"."PUBLIC"."TMW_TRACTORPROFILE" C
ON B.Vehicle = C.TRC_NUMBER
WHERE NOT EXISTS (SELECT DRIVER_ID FROM "PROD"."PUBLIC"."SG_DRIVER_INCIDENTS" D
WHERE A.DRIVER_ID = D.DRIVER_ID
AND D.TIME BETWEEN '2022-07-01' AND '2022-07-31'
AND SUBSTRING(D.TIME, 0, 10) <= A.REPORT_DATE -- Less than or equal to report date
AND SUBSTRING(D.TIME, 0, 10) > SUBSTRING(DATEADD(week,-1, A.REPORT_DATE), 0, 10) -- Greater than 1 week ago
)
AND A.DRIVER_ID != '' AND A.INCIDENTS = '0'
AND A.REPORT_DATE BETWEEN '2022-07-01' AND '2022-07-31'
--AND B.DRIVER_ID IS NULL --<-- For LEFT JOIN
ORDER BY DRIVER_ID
)
--WHERE INCIDENTS != 0
GROUP BY DRIVER_ID, DRIVER_NAME, CSC
ORDER BY DRIVER_ID
This line:
CASE WHEN SUM(INCIDENTS) = '0' THEN '0' ELSE COUNT(INCIDENTS!='0') END AS INCIDENTS seems to give me the correct number of incidents but when I try and copy it into this line as the Incident Count: (COUNT(INCIDENTS!='0') / SUM(DISTINCT(OBSERVATIONS))) * 100 AS FREQUENCY_PERCENT
like: (COUNT(CASE WHEN SUM(INCIDENTS) = '0' THEN '0' ELSE COUNT(INCIDENTS!='0') END) / SUM(DISTINCT(OBSERVATIONS))) * 100 AS FREQUENCY_PERCENT, I get the following error:
SQL compilation error: Aggregate functions cannot be nested: [SUM(CAST("values".INCIDENTS AS FLOAT))] nested in [COUNT(IFF((SUM(CAST("values".INCIDENTS AS FLOAT))) = (CAST('0' AS FLOAT)), TO_NUMBER('0', 18, 0), COUNT(CAST("values".INCIDENTS != '0' AS BOOLEAN))))]
I have seen examples online of nested Aggregate Functions working. Code examples are appreciated.

Answer 1

The first line:
CASE WHEN SUM(INCIDENTS) = '0' THEN '0' ELSE COUNT(INCIDENTS!='0') END
is a conditional aggreation, simplified to COUNT_IF:
COUNT_IF(INCIDENTS != '0') AS INCIDENTS
The second one:
COUNT_IF(INCIDENTS != '0')/NULLIF(SUM(DISTINCT OBSERVATIONS)),0) * 100
AS FREQUENCY_PERCENT
It is always good to secure against division by 0, thus NULLIF(exp, 0).