How can we do update,delete,insert in single merge - oracle

Question

I have a source and target table. I was doing a simple merge where I was able to do insert and update operation simultaneously. I just added columns like insert date and update date to know when the record is inserted and updated. Then, I also added a flag columns which tells us that if the record is ever updated if yes then 'Y' else 'N'. I was successful till this but when I tried to use delete it doesn't allow me.I have seen many solutions in sql server but mine is oracle. I was doing a soft delete in which the record is not deleted from the target but just the flag column is updated to 'Y' if some record is deleted from the source table. But I was not able to do that. I used case also but of no use.To be clear I just want to update flag when there is delete in source. Can anybody tell me how can I do that with single merge statement? I have simple table student having attribute like name,address mobile no , state. I have made my query like this-
merge into target t using (SELECT CASE WHEN S.STUDENT_ID IS NULL THEN T.STUDENT_ID ELSE S.STUDENT_ID END
AS STUDENT_ID,S.NAME,S.ADRESS,S.STATE,S.MOBILE FROM STUDENTS S full JOIN TARGET T ON S.STUDENT_ID=T.STUDENT_ID) s
on (s.student_id = t.student_id)
when not matched then insert (student_id,name,address,state,mobile,insert_date,update_date)
values(s.student_id,s.name,s.adress,s.state,s.mobile,sysdate,sysdate)
when matched then update set t.name=s.name,t.address=s.adress, t.state=s.state,t.mobile=s.mobile,update_date=sysdate
where s.name!=t.name or s.adress!=t.address or s.state!=t.state or s.mobile!=t.mobile;
this time I used case with every attribute and I am able to solve it but every time I run it it shows the no of extra rows present in target merged like - 4 rows are merged I dont want that can anyone help my query is-
MERGE INTO TARGET T USING (SELECT CASE WHEN S.STUDENT_ID IS NULL THEN T.STUDENT_ID ELSE S.STUDENT_ID END
AS STUDENT_ID,S.NAME,S.ADRESS,S.STATE,S.MOBILE FROM STUDENTS S FULL JOIN TARGET T ON S.STUDENT_ID=T.STUDENT_ID) S
ON (S.STUDENT_ID=T.STUDENT_ID)
WHEN NOT MATCHED THEN INSERT
(STUDENT_ID,NAME,ADDRESS,STATE,MOBILE,INSERT_DATE,UPDATE_DATE,FLAG )
VALUES(S.STUDENT_ID,S.NAME,S.ADRESS,S.STATE,S.MOBILE,SYSDATE,SYSDATE, 'N')
WHEN MATCHED THEN UPDATE SET T.FLAG='Y' , t.name = case when s.name is null then T.NAME else S.name end ,
T.ADDRESS=case when s.ADRESS is null then T.ADDRESS else S.ADRESS end ,
t.STATE=case when s.STATE is null then T.STATE else S.STATE end ,
T.MOBILE=CASE WHEN S.MOBILE IS NULL THEN T.MOBILE ELSE S.MOBILE END
WHERE S.NAME!=T.NAME OR S.ADRESS!=T.ADDRESS OR S.STATE!=T.STATE OR S.MOBILE!=T.MOBILE or t.STUDENT_ID in
(SELECT TARGET.STUDENT_ID FROM
STUDENTS FULL JOIN TARGET ON STUDENTS.STUDENT_ID=TARGET.STUDENT_ID WHERE STUDENTS.STUDENT_ID IS NULL);

Answer 1

Answer to my question-
MERGE INTO TARGET T USING
(SELECT CASE
WHEN S.STUDENT_ID IS NULL THEN T.STUDENT_ID
ELSE S.STUDENT_ID
END AS STUDENT_ID,
S.NAME,
S.ADRESS,
S.STATE,
S.MOBILE
FROM STUDENTS S
FULL JOIN TARGET T ON S.STUDENT_ID=T.STUDENT_ID) S ON (S.STUDENT_ID=T.STUDENT_ID) WHEN NOT MATCHED THEN
INSERT (STUDENT_ID,
NAME,
ADDRESS,
STATE,
MOBILE,
INSERT_DATE,
UPDATE_DATE,
FLAG)
VALUES(S.STUDENT_ID,
S.NAME,
S.ADRESS,
S.STATE,
S.MOBILE,
SYSDATE,
SYSDATE,
'N') WHEN MATCHED THEN
UPDATE
SET T.FLAG= CASE
WHEN ( T.STUDENT_ID IN (SELECT TARGET.STUDENT_ID
FROM STUDENTS
FULL JOIN TARGET ON STUDENTS.STUDENT_ID=TARGET.STUDENT_ID
WHERE STUDENTS.STUDENT_ID IS NULL)) THEN 'Y'
ELSE 'N'
END,
T.NAME = CASE
WHEN S.NAME IS NULL THEN T.NAME
ELSE S.NAME
END,
T.ADDRESS=CASE
WHEN S.ADRESS IS NULL THEN T.ADDRESS
ELSE S.ADRESS
END,
T.STATE=CASE
WHEN S.STATE IS NULL THEN T.STATE
ELSE S.STATE
END,
T.MOBILE=CASE
WHEN S.MOBILE IS NULL THEN T.MOBILE
ELSE S.MOBILE
END,
T.UPDATE_DATE=SYSDATE ,
T.INSERT_DATE=SYSDATE
WHERE S.NAME!=T.NAME
OR S.ADRESS!=T.ADDRESS
OR S.STATE!=T.STATE
OR S.MOBILE!=T.MOBILE
OR T.STUDENT_ID IN
(SELECT TARGET.STUDENT_ID
FROM STUDENTS
FULL JOIN TARGET ON STUDENTS.STUDENT_ID=TARGET.STUDENT_ID
WHERE STUDENTS.STUDENT_ID IS NULL)
AND FLAG!='Y';