Oracle SQL: pick the right values for an update - sql

Question

I have two tables. One contains a list of tickets, one contains all the comments made in each ticket. A ticket has an owner, the comment makers are tracked by their user_id.
I want to set the owners of the tickets to the users that make the first comment. The base of the script is this:
update incident inc
inner join incidentdescription incdes on
inc.inci_id = incdes.inci_id
set inc.owner_id=incdes.user_id;
However, each ticket has several comments. I can track the first comment by the incdes.creationdate. I need to have the oldest one. However, how can I make sure that at the set part, I pick the incdes.user_id from the oldest comment from each ticket?

Answer 1

You can try any one of this in Oracle
Normal Update
UPDATE
INCIDENT
SET
INCIDENT.OWNER_ID =
( SELECT
INCIDENTDESCRIPTION.USER_ID
FROM
INCIDENTDESCRIPTION
WHERE
INCIDENT.OWNER_ID = INCIDENTDESCRIPTION.USER_ID )
WHERE
EXISTS
(SELECT
INCIDENTDESCRIPTION.USER_ID
FROM
INCIDENTDESCRIPTION
WHERE
INCIDENT.OWNER_ID = INCIDENTDESCRIPTION.USER_ID);
Using Inline View (If it is considered updateable by Oracle)
Note: If you face a non key preserved row error add an index to resolve the same to make it update-able
UPDATE
(SELECT
INCIDENT.OWNER_ID AS OLD,
INCIDENTDESCRIPTION.USER_ID AS NEW
FROM
INCIDENT
INNER JOIN
INCIDENTDESCRIPTION
ON INCIDENT.INCI_ID = INCIDENTDESCRIPTION.INCI_ID) T
SET
T.OLD = T.NEW;
Using Merge
MERGE INTO
INCIDENT
USING
(SELECT
T1.ROWID AS RID,
T2.INCI_ID
FROM
INCIDENT T1
INNER JOIN
INCIDENTDESCRIPTION T2
ON INCIDENT.INCI_ID = INCIDENTDESCRIPTION.INCI_ID)
ON
( ROWID = RID )
WHEN MATCHED
THEN
UPDATE SET INCIDENT.INCI_ID = INCIDENTDESCRIPTION.INCI_ID;