Oracle Apex - REST data source - nested JSON array - trigger two tables - update function - plsql

Question

This question is a follow up to another SO question.
I've followed Carsten's instructions on the previous question. The trigger works as expected. I now just need to figure out how to handle the updating function of the trigger.
create or replace trigger "TR_MAINTAIN_LINES"
AFTER
insert or update or delete on "ORDERS_LOCAL"
for each row
begin
if inserting then
insert into ORDER_ITEMS_LOCAL ( order_id, line_id, line_number, product_id, quantity, price)
( select :new.order_id,
seq_line_id.nextval,
j.line_number,
j.product_id,
j.quantity,
j.price
from json_table(
:new.order_items,
'$[*]' columns (
line_id for ordinality,
line_number number path '$.line_number',
product_id number path '$.product_id',
quantity number path '$.quantity',
price number path '$.price' ) ) j );
elsif deleting then
delete ORDER_ITEMS_LOCAL
where order_id = :old.order_id;
elsif updating then
delete ORDER_ITEMS_LOCAL
where order_id = :old.order_id;
--
-- handle the update case here.
-- I would simply delete and re-insert ORDER_ITEMS rows.
end if;
end;
Carsten did mention in his answer to a previous question:
"In the UPDATING case, :old.{column-name} references the value of a table column column before the update, :new.{column-name} references the value after the update."
Would I leave the delete line? :
elsif updating then
delete ORDER_ITEMS_LOCAL
where order_id = :old.order_id;
--
-- handle the update case here.
-- I would simply delete and re-insert ORDER_ITEMS rows.
Is the pseudo-code below the correct way to handle this? :
elsif updating then
delete ORDER_ITEMS_LOCAL
where order_id = :old.order_id;
insert into ORDER_ITEMS_LOCAL ( order_id, line_id, line_number, product_id, quantity, price)
( select :new.order_id,
seq_line_id.nextval,
:new.line_number,
:new.product_id,
:new.quantity,
:new.price )

Answer 1

I'm assuming that the update could potentially mean a new json value in ORDERS_LOCAL.ORDER_ITEMS. In that case the json needs to be parsed just like for the insert. Combine both inserting and deleting in a single if statement to avoid duplicate code.
create or replace trigger "TR_MAINTAIN_LINES"
AFTER
insert or update or delete on "ORDERS_LOCAL"
for each row
begin
if inserting or updating then
if updating then
delete ORDER_ITEMS_LOCAL
where order_id = :old.order_id;
end if;
insert into ORDER_ITEMS_LOCAL ( order_id, line_id, line_number, product_id, quantity, price)
( select :new.order_id,
seq_line_id.nextval,
j.line_number,
j.product_id,
j.quantity,
j.price
from json_table(
:new.order_items,
'$[*]' columns (
line_id for ordinality,
line_number number path '$.line_number',
product_id number path '$.product_id',
quantity number path '$.quantity',
price number path '$.price' ) ) j );
elsif deleting then
delete ORDER_ITEMS_LOCAL
where order_id = :old.order_id;
end if;
end;