带有计数的Oracle独特的listagg

Question

I need to display a comma-separated description per table row but I need the list to be distinct and have counts for some of the descriptions available.

every_description     needs_count
---------------------------------
Bred                          yes
From Vendor                   yes
Grouped                        no
Removed                       yes
Separated                      no
Weaned                        yes

So in a day, the description could be something like Bred, Grouped, Weaned and I have this working now using LISTAGG and removing the duplicates using the solution mentioned here but I need to add counts for some of the descriptions like 5 Bred, Grouped, 2 Weaned .

Here's my current query where I'm stuck:

WITH cages AS (
        SELECT 1234 AS id FROM DUAL
  UNION SELECT 5678 AS id FROM DUAL
  UNION SELECT 9012 AS id FROM DUAL
  UNION SELECT 3456 AS id FROM DUAL
), cage_comments AS (
        SELECT 1234 AS cage_id, 'Bred' AS description, TO_DATE('11/14/2017', 'MM/DD/YYYY') AS event_date FROM DUAL
  UNION SELECT 5678 AS cage_id, 'Grouped' AS description, TO_DATE('11/14/2017', 'MM/DD/YYYY') AS event_date FROM DUAL
  UNION SELECT 9012 AS cage_id, 'Weaned' AS description, TO_DATE('11/14/2017', 'MM/DD/YYYY') AS event_date FROM DUAL
  UNION SELECT 3456 AS cage_id, 'Weaned' AS description, TO_DATE('11/14/2017', 'MM/DD/YYYY') AS event_date FROM DUAL
  UNION SELECT 3456 AS cage_id, 'Bred' AS description, TO_DATE('11/02/2017', 'MM/DD/YYYY') AS event_date FROM DUAL
  UNION SELECT 3456 AS cage_id, 'Grouped' AS description, TO_DATE('11/14/2017', 'MM/DD/YYYY') AS event_date FROM DUAL
), calendar AS (
  SELECT dt
  FROM (
    SELECT TRUNC(LAST_DAY(TO_DATE(&month || '/01/' || &year, 'MM/DD/YYYY')) - ROWNUM + 1) dt
    FROM DUAL CONNECT BY ROWNUM <= 31
  )
  WHERE dt >= TRUNC(TO_DATE(&month || '/01/' || &year, 'MM/DD/YYYY'), 'MM')
  ORDER BY dt ASC
)

SELECT
  cal.dt,
  (
    SELECT
      CASE
        WHEN COUNT(cc.cage_id) > 0 THEN RTRIM(
          REGEXP_REPLACE(
            (LISTAGG(cc.description, ',') WITHIN GROUP (ORDER BY cc.description)),
            '([^,]*)(,\1)+($|,)',
            '\1\3'
          ),
          ','
        )
        ELSE NULL
      END
    FROM cages c
    LEFT JOIN cage_comments cc ON cc.cage_id = c.id
    WHERE cc.event_date = cal.dt
  ) AS description
FROM calendar cal
ORDER BY cal.dt

---

In short - I'm just having difficulties adding the COUNT for some of the descriptions for that day. In the case above I would like to say 1 Bred for November 2, 2017 and 1 Bred, Grouped, 2 Weaned for November 14, 2017 .

Answer 1

Currently you are aggregating all the descriptions (without DISTINCT) and then you remove the duplicate descriptions with a regular expression replace. This is very inefficient - it would be better to select distinct and then apply LISTAGG.

This becomes even more important if you need to add the count. Take the result of your join and GROUP BY description. (In particular, this will take care of DISTINCT). In the SELECT for this aggregate step, include the count. Then join the result to the additional table at the top of your question, and re-write the argument to LISTAGG to include a CASE expression, equal to the count (and a space) when the needs_count value is 'yes' .

Answer 2

You could use:

SELECT
  cal.dt,
  ( 
      SELECT LISTAGG(CASE WHEN COUNT(*)=1 THEN '' 
            ELSE CAST(COUNT(*) AS VARCHAR2(10)) || ' ' END  || description, ', ')
            WITHIN GROUP (ORDER BY description) 
      FROM cages c
      LEFT JOIN cage_comments cc ON cc.cage_id = c.id
      WHERE cc.event_date = cal.dt
      GROUP BY cc.event_date, cc.description
  ) AS description
FROM calendar cal
ORDER BY cal.dt;

DBFiddle Demo