SQL使用listagg（）并按非重复值分组

Question

        ID TELNO
---------- --------------------
         1 0123456789
         1 0207983498
         2 0124339848
         2 09348374834
         2 02387694364

How can i query the above table to get output like this:

        ID TEL_LIST
---------- --------------------
         1 0123456789,0207983498
         2 0124339848,09348374834,09348374834 

I know i can use the listagg() to concatenate the id's by grouping the columns. For example,

listagg(id',') within group (order by id) as idList

will return 1,2.

The TELNO column however cannot be grouped and the values are usually unique. How to do the concatenation on the second column where a group by is not possible?

Answer 1

Query:

SQLFIDDLEEXAMPLE

SELECT 
ID, LISTAGG(TELNO, ', ') 
WITHIN GROUP (ORDER BY TELNO) 
AS TEL_LIST
FROM   tbl
GROUP BY ID;

Result:

| ID |                             TEL_LIST |
---------------------------------------------
|  1 |               0123456789, 0207983498 |
|  2 | 0124339848, 02387694364, 09348374834 |

Answer 2

I Don't know whether you have put a unique constraint on ID,TELNO or not .If not ,we need to filter the unique values from the Table first and then apply LISTAGG as shown below:

  SELECT ID,
       LISTAGG(TELNO, ',') WITHIN GROUP (ORDER BY ID) AS TELNO
  FROM (
       SELECT UNIQUE
              ID,
              TELNO
         FROM tbl
       )
  GROUP BY ID;

SQLFIDDLE: LINK

If you look to the execution place or the trace file ,the cost will be the same on the same set of data, with query JUSTIN suggested in the above solution

Answer 3

您可以使用wm_concat（）函数执行相同的操作。

 select id,wm_concat(telno) from my_table group by id;