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Question

I would like to update a table by referencing values within it's own row and also it's parent record in the same table.

I have a table called import, and it needs to update the child record's chain_id to it's parent's chain_id if its currently set to 0 and the parent isn't 0. Also set the child records status to 1 if the action is 3 otherwise leave it as it was, and also set the parent status to 0.

Here is some non-working code that illustrates what I'm trying to do:

update 
(
select
c.chain_id as c_chain_id,
c.status as c_status,
c.action as c_action,
p.chain_id as p_chain_id,
p.status as p_status
from import c
join import p on c.original_dissemination_id = p.dissemination_id
where c.chain_id = 0 and
p.chain_id <> 0 and
)
set
c_chain_id = p_chain_id,
c_status = (if c_action = 3 then return 1 else c_status), /* 3 if action = 1 else leave it as it was */
p_status = 0

Can someone please translate the above to some oracle code that works? thanks

Answer 1

Do you tried to fix it with hierarchical queries?

See this examples:

   http://docs.oracle.com/cd/B19306_01/server.102/b14200/queries003.htm

Regards and good luck

Answer 2

The problem I see is you're wanting preform 2 updates at the same time. Effectively, what you have are two tables c and p with a hierarchical relation. I don't know of a sql only way in oracle to update 2 tables at once. There are some tricks you could do with views and possibly some really fancy SQL.

However, fancy is not always the best solution.

I would recommend using a little pl/sql such as

BEGIN
  FOR v_rec IN (SELECT c.chain_id AS c_chain_id,
                     c.status AS c_status,
                     c.action AS c_action,
                     p.chain_id AS p_chain_id,
                     p.status AS p_status,
                     c.dissemination_id AS c_dissemination_id,
                     p.dissemination_id AS p_dissemination_id
                FROM import c
                JOIN import p ON c.original_dissemination_id = p.dissemination_id
               WHERE c.chain_id = 0
                 AND p.chain_id <> 0) LOOP

    UPDATE import
       SET chain_id = v_rec.p_chain_id,
           status = decode(v_rec.c_action, 3, 1, status)
     WHERE dissemination_id = v_rec.c_dissemination_id;

    UPDATE import
       SET chain_id = 0
     WHERE dissemination_id = v_rec.p_dissemination_id;

    commit;

  END LOOP;

END;
/

This should loop through all the records as you defined in your query above (I added what I'm assuming are the pk and fk columns to the output.) This will do the 2 updates and the decode will handle the action/status part.

You'll of course, want to test this and put some exception handling in as needed.