Oracle SQL XMLAGG &quote; Issue - sql

Question

I am trying to aggregate A into a list of dictionaries. Oracle's LISTAGG() works but does run into the 4k max char limit. I tried with XMLAGG but now I'm getting "and quot;" instead of "". Please suggest the best way of resolving this. XMLCAST ? Will the final outputs of listagg() and the work around be identical ?
A
N
{"1":"09","2":"11","3":"2010","4":"XYZ","5":""}
1
{"1":"09","2":"11","3":"2010","4":"XYZ","6":""}
2
{"1":"09","2":"11","3":"2010","4":"XYZ","7":""}
3
select
-- '[' ||
-- LISTAGG(cte.A, ' , ') WITHIN GROUP(
-- ORDER BY
-- cte.N
-- )
-- || ']'
'[' ||
rtrim(xmlagg(xmlelement(e,cte.A,', ').extract('//text()') order by cte.N).getclobval(),', ')
|| ']' aggr_lsts
from cte;
Bad Output:
[{"1":"09","2":"11","3":"2010","4":"XYZ","5":""}, {"1":"09","2":"11","3":"2010","4":"XYZ","6":""}, {"1":"09","2":"11","3":"2010","4":"XYZ","7":""}]
Good Output:
[{"1":"09","2":"11","3":"2010","4":"XYZ","5":""} , {"1":"09","2":"11","3":"2010","4":"XYZ","6":""} , {"1":"09","2":"11","3":"2010","4":"XYZ","7":""}]
Thank you.

Answer 1

You may use xmlcast function to correctly deserialize XML data as a clob.
Please note, that XMLType methods are deprecated since Oracle 11.2, so use XMLQUERY and XMLCAST instead.
with sample(col, rn) as (
select column_value, rownum
from sys.odcivarchar2list(
'&',
'>',
'<',
'"',
'correctly serializable text'
)
)
select
rtrim(xmlcast(xmlquery(
'//text()'
passing xmlagg(
xmlelement(e,col,', ')
order by rn
)
returning content
) as clob), ', ') as res
from sample
RES
&, >, <, ", correctly serializable text
But for 12.2 and above you may use JSON functions directly to produce correct JSON array: JSON_ARRAYAGG (with a restriction on 32k JSON keys per object, if I remember correctly).
with sample(col, rn) as (
select column_value, rownum
from sys.odcivarchar2list(
'{"a": 1, "b": "2"}',
'{"a": 2, "b": "qwe"}',
'{"a": 3, "c": "test"}'
)
)
select
json_arrayagg(
col order by rn
) as res
from sample
RES
["{"a": 1, "b": "2"}","{"a": 2, "b": "qwe"}","{"a": 3, "c": "test"}"]
fiddle

Answer 2

Don't use XML functions with JSON data. From Oracle 12.2, use JSONAGG to aggregate the rows:
SELECT JSON_ARRAYAGG(a FORMAT JSON ORDER BY n RETURNING CLOB) As output
FROM table_name
Note: you need FORMAT JSON to treat your input as valid JSON, otherwise it will be treated as a string and quoted. You also need RETURNING CLOB otherwise the default return type is a VARCHAR2 which is limited to 4000 characters and will give you the same issues as LISTAGG.
Which, for the sample data:
CREATE TABLE table_name (A, N) AS
SELECT '{"1":"09","2":"11","3":"2010","4":"XYZ","5":""}', 1 FROM DUAL UNION ALL
SELECT '{"1":"09","2":"11","3":"2010","4":"XYZ","6":""}', 2 FROM DUAL UNION ALL
SELECT '{"1":"09","2":"11","3":"2010","4":"XYZ","7":""}', 3 FROM DUAL;
Outputs:
OUTPUT
[{"1":"09","2":"11","3":"2010","4":"XYZ","5":""},{"1":"09","2":"11","3":"2010","4":"XYZ","6":""},{"1":"09","2":"11","3":"2010","4":"XYZ","7":""}]
fiddle