Merge statment doesnt work

Question

Hi all.
I have 2 tables for the merge:
CREATE TABLE DAM_ACCESOS_LASTLOGIN
FECHA DATE,
USUARIO VARCHAR2(100)
TABLESPACE COLOSO
CREATE TABLE DAM_ACCESOS_LASTLOGIN_STAGE
FECHA DATE,
USUARIO VARCHAR2(100)
TABLESPACE COLOSO
Atm DAM_ACCESOS_LASTLOGIN is empty and i im trying to populate it with the data from DAM_ACCESOS_LASTLOGIN_STAGE. For that im using a merge statment like this:
merge into dam_accesos_lastlogin f
using dam_accesos_lastlogin_stage s
on (f.usuario=s.usuario)
when matched then
update set f.fecha=s.fecha
when not matched
then insert (f.fecha,f.usuario)
values (s.fecha,s.usuario);
The DAM_ACCESOS_LASTLOGIN_STAGE have 29 millions rows, and sql said only 2millions have been merged. But when i select DAM_ACCESOS_LASTLOGIN instead of date,user only one time i have the same user with distinct dates.
For example:
30/10/2007|[email protected]
01/11/2007|[email protected]
28/10/2007|[email protected]
26/10/2007|[email protected]
24/10/2007|[email protected]
23/10/2007|[email protected]
25/10/2007|[email protected]
21/10/2007|[email protected]
22/10/2007|[email protected]
29/10/2007|[email protected]
16/10/2007|[email protected]
04/11/2007|[email protected]
Im trying to have only one date and one user on DAM_ACCESOS_LASTLOGIN , and update the date if the user existes in DAM_ACCESOS_LASTLOGIN_STAGE, but dunno why dont work
In DAM_ACCESOS_LASTLOGIN_STAGE i have same user, diferent dates and in DAM_ACCESOS_LASTLOGIN only want one date x user.
Any help will be awesome.
Thanks
Message was edited by:
user496863

Answer 1

The merge statement does not row by row processing, it is doing all at once.
If you have the same user multiple times in your start table DAM_ACCESOS_LASTLOGIN_STAGE, then it will insert it multiple times.
To avoid it you should select each user only once, e.g.:
merge into dam_accesos_lastlogin f
using (select usuario, max(fecha) fecha from dam_accesos_lastlogin_stage group by usario) s
on (f.usuario=s.usuario)
when matched then
update set f.fecha=s.fecha
when not matched
then insert (f.fecha,f.usuario)
values (s.fecha,s.usuario);Btw: I like the name of your tablespace! COLOSO is much better than my usual DATA_HUGE.