我们如何在单个合并中进行更新，删除，插入

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';