Insert / update with subquery

Question

Hi,
i have to insert (if records don't exist) or update (if records already exist) records from table S into table D. S and D have the same structure.
Table S
ID NUMBER, Primary Key,
DESC1 VARCHAR
DESC2 VARCHAR
Table D
ID NUMBER, Primary Key,
DESC1 VARCHAR
DESC2 VARCHAR
Are this statements OK?
INSERT INTO D
( SELECT * FROM S T1 WHERE NOT EXISTS
( SELECT '1' FROM D T2 WHERE T2.ID = T1.ID));
UPDATE D T1
SET (DESC1, DESC2) =
(SELECT DESC1, DECS2
FROM S T2 WHERE T1.ID = T2.ID ) WHERE EXIST
( SELECT '1' FROM S T3 WHERE T1.ID = T3.ID );
Thanks a lot

Answer 1

Depends on exist or not the data in
the destination where id doesn't exists in the source.
SQL> select * from updatable_tab;
ID DESC1 DESC2
1 0 0
1 0 0
1 0 0
1 0 0
2 f f
2 f f
2 f f
2 f f
2 f f
9 rows selected.
SQL> update updatable_tab dst set (desc1, desc2) =
2 (select desc1, desc2 from s where s.id = dst.id)
3 /
9 rows updated.
SQL> select * from updatable_tab;
ID DESC1 DESC2
1 A A
1 A A
1 A A
1 A A
2 B B
2 B B
2 B B
2 B B
2 B B
9 rows selected.
But if you have the row in the destination table
wich does not exists in the source table, it will
nullify your dest1 and dest2.
In this case you should of course:
SQL> select * from updatable_tab;
ID DESC1 DESC2
1 0 0
1 0 0
1 0 0
1 0 0
2 f f
2 f f
2 f f
2 f f
2 f f
3 m m
10 rows selected.
SQL> select * from s;
ID DESC1 DESC2
1 A A
2 B B
SQL> update updatable_tab dst set (desc1, desc2) =
2 (select desc1, desc2 from s where s.id = dst.id)
3 where exists (select null from s where s.id = dst.id)
4 /
9 rows updated.
SQL> select * from updatable_tab;
ID DESC1 DESC2
1 A A
1 A A
1 A A
1 A A
2 B B
2 B B
2 B B
2 B B
2 B B
3 m m
Rgds.