oracle lookup translation for a column value - sql

Question

I have a table with data below
create table A
(id number,
code varchar2(100));
insert into A values
(1, '20,21,22');
insert into A values
(2, '22,23,24');
commit;
create table code_descriptions
(
code_id number,
code_desc varchar2(100));
insert into code_descriptions values
(20, 'ABC');
insert into code_descriptions values
(21, 'BBC');
insert into code_descriptions values
(22, 'CAP');
insert into code_descriptions values
(23, 'INC');
insert into code_descriptions values
(24, 'ABC');
commit;
I would like to come up with sql to update table A code values with descriptions
Could you please suggest any functions or ideas, to achieve this?

Answer 1

You can tokenize your comma-separated lists:
select id, level as rn, regexp_substr(code, '(.*?)(,|$)', 1, level, null, 1) as code_id
from a
connect by level <= regexp_count(code, ',') + 1
and id = prior id
and prior dbms_random.value is not null;
ID RN CODE_ID
---------- ---------- -------
1 1 20
1 2 21
1 3 22
2 1 22
2 2 23
2 3 24
Then use that as a CTE (subquery factoring) and join to the descriptions (I've made it a left-join so you choose how to handle any missing codes):
with cte (id, rn, code_id) as (
select id, level, regexp_substr(code, '(.*?)(,|$)', 1, level, null, 1)
from a
connect by level <= regexp_count(code, ',') + 1
and id = prior id
and prior dbms_random.value is not null
)
select cte.id, cte.rn, cte.code_id, coalesce(cd.code_desc, '??') as code_desc
from cte
left join code_descriptions cd on cd.code_id = cte.code_id;
ID RN CODE_ID CODE_DESC
---------- ---------- ------- ---------
1 1 20 ABC
1 2 21 BBC
2 1 22 CAP
1 3 22 CAP
2 2 23 INC
2 3 24 ABC
and then aggregate those back into single comma-separated values:
with cte (id, rn, code_id) as (
select id, level, regexp_substr(code, '(.*?)(,|$)', 1, level, null, 1)
from a
connect by level <= regexp_count(code, ',') + 1
and id = prior id
and prior dbms_random.value is not null
)
select cte.id,
listagg(coalesce(cd.code_desc, '??'), ',') within group (order by rn) as code
from cte
left join code_descriptions cd on cd.code_id = cte.code_id
group by cte.id;
ID CODE
---------- ----------------
1 ABC,BBC,CAP
2 CAP,INC,ABC
and then merge or us a correlated update:
update a
set code = (
with cte (id, rn, code_id) as (
select id, level, regexp_substr(code, '(.*?)(,|$)', 1, level, null, 1)
from a
connect by level <= regexp_count(code, ',') + 1
and id = prior id
and prior dbms_random.value is not null
)
select listagg(coalesce(cd.code_desc, '??'), ',') within group (order by rn) as code
from cte
left join code_descriptions cd on cd.code_id = cte.code_id
where cte.id = a.id
group by cte.id
);
2 rows updated.
select * from a;
ID CODE
---------- ----------------
1 ABC,BBC,CAP
2 CAP,INC,ABC
or
rollback; -- just to undo previous update
merge into a
using (
with cte (id, rn, code_id) as (
select id, level, regexp_substr(code, '(.*?)(,|$)', 1, level, null, 1)
from a
connect by level <= regexp_count(code, ',') + 1
and id = prior id
and prior dbms_random.value is not null
)
select cte.id, listagg(coalesce(cd.code_desc, '??'), ',') within group (order by rn) as code
from cte
left join code_descriptions cd on cd.code_id = cte.code_id
group by cte.id
) tmp
on (tmp.id = a.id)
when matched then update set a.code = tmp.code;
2 rows merged.
select * from a;
ID CODE
---------- ----------------
1 ABC,BBC,CAP
2 CAP,INC,ABC
db<>fiddle

Answer 2

The simplest solution is if the number of elements in the "code" column of table A is fixed - by directly gluing the subqueries to the code_descriptions table by codes (we cut each code from the enumeration line).