Oracle Query to update substring of column value - oracle

Question

We have 2 tables as shown below:
Table A:
ROWNUM
description
1
{"to": "+1111", "from": "9999"}
2
{"to": "+5555", "from": "8888"}
Table B:
COL1
COL2
+1111
222
+5555
666
Please help me with an Oracle query which replaces part of the description column present in Table A from above table.
The numbers present after text "to:" i.e., +1111 and +5555 of Table A (description column)should be compared with COL1 of Table B and replace with corresponding COL2 value.
For example : replace +1111 with 222 in Table A
replace +5555 with 666 in Table A
Table A should look like this post running of the query.
Table A:
ROWNUM
description
1
{"to": "222", "from": "9999"}
2
{"to": "666", "from": "8888"}
Thanks in advance :)

Answer 1

You can use techniques dedicated to JSON within a PL/SQL code values such as
DECLARE
v_jsoncol tableA.description%TYPE;
v_json_obj json_object_t;
v_new_jsoncol tableA.description%TYPE;
v_col1 tableB.col1%TYPE;
v_col2 VARCHAR2(25);
l_key_list json_key_list;
BEGIN
FOR c IN
(
SELECT *
FROM tableA
)
LOOP
v_json_obj := TREAT(json_element_t.parse(c.description) AS json_object_t);
l_key_list := v_json_obj.get_keys;
FOR i IN 1 .. l_key_list.COUNT
LOOP
IF l_key_list (i) = 'to' THEN
v_col1 := v_json_obj.get_string (l_key_list (i));
SELECT TO_CHAR(col2)
INTO v_col2
FROM tableB
WHERE col1 = v_col1;
v_json_obj.put(l_key_list (i),v_col2);
v_new_jsoncol := v_json_obj.to_string;
UPDATE tableA SET description = v_new_jsoncol WHERE row_num = c.row_num;
END IF;
END LOOP;
END LOOP;
END;
/
Demo

Answer 2

I used instr to get 3rd and 4th " chars position to get the value inside and replace it with other query .
Note : ROWNUM , description is reserved keywords, so i advise not to use them as column names
here is the final code:
SELECT ROWNUM ,
REPLACE (description ,
SUBSTR( description , INSTR(description, '"', 1, 3)+1,
INSTR(description, '"', 1, 4) - INSTR(description, '"', 1, 3)-1) ,
(select COL2 from tblB where COL1 =
SUBSTR( description , INSTR(description, '"', 1, 3)+1,
INSTR(description, '"', 1, 4) - INSTR(description, '"', 1, 3)-1)
)
)
from tblA

Answer 3

Don't use string functions for this. You should use JSON functions and can use JSON_MERGEPATCH:
MERGE INTO table_a dst
USING (
SELECT a.ROWID AS rid,
b.col2
FROM table_a a
INNER JOIN table_b b
ON JSON_VALUE(a.description, '$.to' RETURNING VARCHAR2(10)) = b.col1
) src
ON (dst.ROWID = src.RID)
WHEN MATCHED THEN
UPDATE
SET description = JSON_MERGEPATCH(
dst.description,
JSON_OBJECT(KEY 'to' VALUE src.col2)
);
Which, for your sample data:
CREATE TABLE Table_A (description CLOB CHECK (description IS JSON));
INSERT INTO table_a (description)
SELECT '{"to": "+1111", "from": "9999"}' FROM DUAL UNION ALL
SELECT '{"to": "+5555", "from": "8888"}' FROM DUAL;
CREATE TABLE Table_B (COL1, COL2) AS
SELECT '+1111', 222 FROM DUAL UNION ALL
SELECT '+5555', 666 FROM DUAL;
Then:
SELECT * FROM table_a;
Outputs:
DESCRIPTION
{"to":222,"from":"9999"}
{"to":666,"from":"8888"}
db<>fiddle here