Aggregation in UPDATE SQL query - sql

Question

So, I have currently have two tables, one containing the fixed part of each object, and the other containing a variable number of properties of each object as key/value pairs. I would like to convert these properties to a CLOB field in the main table in JSON map format.
create table test_a (id integer, properties clob);
create table test_b (id integer, a_id integer, key char(30), value char(30));
insert into test_a values(1,'');
insert into test_a values(2,'');
insert into test_a values(3,'');
insert into test_b values (1, 1, 'k1', 'v1');
insert into test_b values (2, 1, 'k2', 'v2');
insert into test_b values (3, 2, 'k3', 'v3');
insert into test_b values (4, 2, 'k4', 'v4');
insert into test_b values (5, 2, 'k5', 'v5');
insert into test_b values (6, 2, 'k6', 'v6');
I can build the JSON I want via the following query:
WITH PROPS AS
(SELECT '"'
||trim(KEY)
||'":"'
||trim(value)
||'"' json,
test_b.*
FROM test_b
)
SELECT test_a.id,
'{'
||
(SELECT listagg(json, ',') within GROUP (
ORDER BY props.key)
FROM PROPS
WHERE PROPS.A_ID = test_a.id
)
|| '}'
FROM TEST_A
INNER JOIN PROPS
ON TEST_A.ID = PROPS.A_ID
GROUP BY TEST_A.ID ;
And I get the desired result
1 "{""k1"":""v1"",""k2"":""v2""}"
2 "{""k3"":""v3"",""k4"":""v4"",""k5"":""v5"",""k6"":""v6""}"
But when I try to use this result to insert into the master table, I get errors
UPDATE TEST_A SET PROPERTIES = (
WITH PROPS AS
(SELECT '"'
||trim(key)
||'":"'
||trim(value)
||'"' json,
test_b.*
FROM test_b
)
SELECT '{'
||
(SELECT listagg(json, ',') within GROUP (order by props.key) FROM PROPS
WHERE PROPS.A_ID = test_a.id)
|| '}' from TEST_A INNER JOIN PROPS ON TEST_A.ID = PROPS.A_ID GROUP BY TEST_A.ID
) ;
Error report -
SQL Error: ORA-01427: single-row subquery returns more than one row
01427. 00000 - "single-row subquery returns more than one row"
Any ideas?

Answer 1

You need a correlated subquery rather than a group by. The entire outer query doesn't look right, so I think you need something like:
UPDATE TEST_A
SET PROPERTIES = (
WITH PROPS AS (
SELECT '"'||trim(key)||'":"'||trim(value)||'"' as json,
test_b.*
FROM test_b
)
SELECT '{' || listagg(json, ',') within GROUP (order by props.key) || '}'
FROM PROPS
WHERE PROPS.A_ID = test_a.id
) ;