When doing a MERGE in Oracle SQL, how can I update rows that aren't matched in the SOURCE?

Question

I have a main database and a report database, and I need to sync a table from main into report.

However, when an item gets deleted in the main database, I only want to set an IsDeleted flag in the report database.

What is an elegant way to do this?

I'm currently using a MERGE statement, like this:

MERGE INTO report.TEST target
USING (SELECT * FROM main.TEST) source
   ON (target.ID = source.ID)
WHEN MATCHED THEN
    UPDATE SET (target... = source...)
WHEN NOT MATCHED THEN
    INSERT (...) VALUES (source...)
;

The WHEN NOT MATCHED statement gives me all NEW values from main, but I also want to update all OLD values from report.

I'm using Oracle PL/SQL.

Solution 1

You can do it with a separate UPDATE statement

UPDATE report.TEST target
SET    is Deleted = 'Y'
WHERE  NOT EXISTS (SELECT 1
                   FROM   main.TEST source
                   WHERE  source.ID = target.ID);

I don't know of any way to integrate this into your MERGE statement.

Solution 2

The following answer is to merge data into same table

MERGE INTO YOUR_TABLE d
USING (SELECT 1 FROM DUAL) m
    ON ( d.USER_ID = '123' AND d.USER_NAME= 'itszaif') 
WHEN NOT MATCHED THEN
        INSERT ( d.USERS_ID, d.USER_NAME)
        VALUES ('123','itszaif');

This command checks if USER_ID and USER_NAME are matched, if not matched then it will insert.

Solution 3

MERGE INTO target
USING
(
    --Source data
    SELECT id, some_value, 0 deleteMe FROM source
    --And anything that has been deleted from the source
    UNION ALL
    SELECT id, null some_value, 1 deleteMe
    FROM
    (
        SELECT id FROM target
        MINUS
        SELECT id FROM source
    )
) source
   ON (target.ID = source.ID)
WHEN MATCHED THEN
    --Requires a lot of ugly CASE statements, to prevent updating deleted data
    UPDATE SET target.some_value =
        CASE WHEN deleteMe=1 THEN target.some_value ELSE source.some_value end
    ,isDeleted = deleteMe
WHEN NOT MATCHED THEN
    INSERT (id, some_value, isDeleted) VALUES (source.id, source.some_value, 0)

--Test data
create table target as
select 1 ID, 'old value 1' some_value, 0 isDeleted from dual union all
select 2 ID, 'old value 2' some_value, 0 isDeleted from dual;

create table source as
select 1 ID, 'new value 1' some_value, 0 isDeleted from dual union all
select 3 ID, 'new value 3' some_value, 0 isDeleted from dual;


--Results:
select * from target;

ID  SOME_VALUE   ISDELETED
1   new value 1  0
2   old value 2  1
3   new value 3  0

Comments

[Scott Rippey]

It seems weird that I can't do this with MERGE. I'll consider this answer.

[Scott Rippey]

Would it be any more "elegant"/efficient if I did an OUTER JOIN, and updated where main.test is null?

[steve godfrey]

There's a related question here stackoverflow.com/questions/4863960/…, I think it'll do an outer join, not a full outer join, so I don't think what you've suggested will work.

[Scott Rippey]

Thank you so much, that link was very helpful What I learned: if MERGE only has WHEN MATCHED THEN, it uses a regular JOIN. If there's a WHEN NOT MATCHED THEN, it uses a LEFT OUTER JOIN. Now, I'm wishing for a feature such as WHEN NOT MATCHED ON SOURCE THEN, which will do a FULL OUTER JOIN. But this might only exist for SQL Server, not Oracle.

[Scott Rippey]

Thanks for being creative! I'm not gonna do this, but it does get the job done.

[Florin Ghita]

where did you found this syntax? (by target)

[Scott Rippey]

This is exactly what I'm looking for ... however, as @FlorinGhita said, where did you find this syntax? Is this MS SQL syntax?

[user272735]

-1 as this is SQL Server merge syntax not Oracle merge

[Scott Rippey]

Just for everyone's reference, this is a good answer, but not matched by target and not matched by source is a feature only supported by MS SQL Server. This feature would solve my problem, so I wish Oracle SQL supported it.