Question

我需要为每个表行显示逗号分隔的描述，但我需要列表是不同的，并且对某些可用的描述有计数。

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

所以在一天之内，描述可能类似于Bred, Grouped, Weaned，我现在正在使用LISTAGG并使用提到的here解决方案删除重复项，但我需要添加计数对于某些描述，例如5 Bred, Grouped, 2 Weaned。

这是我当前查询的地方：

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

简而言之 - 我在为当天的某些描述添加COUNT时遇到了困难。在上面的例子中，我想对1 Bred说November 2, 2017，为1 Bred, Grouped, 2 Weaned说November 14, 2017。

Answer 1

目前您正在聚合所有描述（没有DISTINCT），然后使用正则表达式替换删除重复描述。这是非常低效的 - 选择distinct然后应用LISTAGG会更好。

如果您需要添加计数，这就变得更加重要。获取您的加入和GROUP BY描述的结果。（特别是，这将照顾DISTINCT）。在SELECT for this aggregate步骤中，包括计数。然后将结果连接到问题顶部的附加表，并将参数重新写入LISTAGG以包含CASE表达式，等于needs_count值为{{1时的计数（和空格） }}

Answer 2

您可以使用：

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;

<强> DBFiddle Demo

带有count的Oracle独特listagg

2 个答案: