SQL LISTAGG最小和最大函数问题

Question

Need to find min and max date inside of list tag Like this in one column Min Date:01/01/2015 / Max Date:01/05/2015

SELECT D.ITEM_ID AS "ItemId",
       C.NAME AS "ItemName",
       D.UOM_ID AS "UomId",
       B.DESCRIPTION AS "Uom",
       sum(D.REQUIRED_QTY) AS "Quantity",
       LISTAGG(A.REASON, ', ') WITHIN GROUP (ORDER BY A.REASON) "ReasonType",
       LISTAGG(D.REQUIRED_DATE, ', ') WITHIN GROUP (ORDER BY D.REQUIRED_DATE) "PoRequiredDate",  
       LISTAGG(D.PO_COMMENT, ', ') WITHIN GROUP (ORDER BY D.PO_COMMENT) "Comment"
FROM BIZZXE_V2_SCH.REASONS A,
     BIZZXE_V2_SCH.UOMS B,
     BIZZXE_V2_SCH.ITEMS C,
     BIZZXE_V2_SCH.PO_REQUEST_ITEMS D,
     BIZZXE_V2_SCH.PO_REQUESTS E
WHERE E.PO_REQUEST_ID=D.PO_REQUEST_ID
  AND D.ITEM_ID=C.ITEM_ID
  AND D.UOM_ID=B.UOM_ID
  AND D.REASON_ID=A.REASON_ID
GROUP BY D.ITEM_ID, C.NAME, D.UOM_ID, B.DESCRIPTION 

Need to add Min dt and Max dt to one column as a "PoRequiredDate"

 WITH DATA AS(
   SELECT  listagg(REQUIRED_DATE, ',') WITHIN GROUP (ORDER BY REQUIRED_DATE) dt
    FROM PO_REQUEST_ITEMS 
  WHERE PO_REQUEST_ID =16

  )
 SELECT dt,
        SUBSTR(dt, 1, instr(dt, ',', 1, 1)-1) min_dt,
         SUBSTR(dt, instr(dt, ',', -1, 1)+1)   max_dt
  FROM data
  /

Answer 1

So you want the MIN and MAX date from the aggregated values of the LISTAGG output.

Since LISTAGG will always have an ordered values , the min date will be the first element in the comma delimited list, and the max date will be the last element in each group .

So, all you need to use is:

• SUBSTR
• INSTR

For example,

SQL> WITH DATA AS(
  2  SELECT deptno, listagg(hiredate, ',') WITHIN GROUP (ORDER BY deptno) dt
  3    FROM emp
  4   WHERE deptno <> 30
  5  GROUP BY deptno
  6  )
  7  SELECT deptno,
  8         dt,
  9         SUBSTR(dt, 1, instr(dt, ',', 1, 1)-1) min_dt,
 10         SUBSTR(dt, instr(dt, ',', -1, 1)+1)   max_dt
 11  FROM data
 12  /

    DEPTNO DT                                                      MIN_DT          MAX_DT
---------- ------------------------------------------------------- --------------- ----------
        10 1981-06-09,1981-11-17,1982-01-23                        1981-06-09      1982-01-23
        20 1980-12-17,1981-04-02,1981-12-03,1982-12-09,1983-01-12  1980-12-17      1983-01-12

SQL>

Answer 2

You could use syntax "KEEP (DENSE_RANK FIRST/LAST...)" for your purpose:

   'Min Date: '||min(REQUIRED_DATE) KEEP (DENSE_RANK FIRST ORDER BY REQUIRED_DATE) ||
' / Max Date: '||min(REQUIRED_DATE) KEEP (DENSE_RANK LAST ORDER BY REQUIRED_DATE NULLS FIRST)

The main issues there are FIRST and LAST keywords - they're aggregate or analytic functions. KEEP indicates that either FIRST or LAST will be used in expression. DENSE_RANK indicates that database will use only those values, which have the minimal (FIRST) or maximal (LAST) dense rank. Dense rank calculation is based on sorting, which is set by ORDER BY clause.

Notice, that in your case it doesn't matter if you use MIN or MAX in main expression. This is because function "KEEP...DENSE_RANK...FIRST/LAST" described above passes to aggregate function (MIN/MAX) only those records, which already have extreme values.