Scd type 1 using pl-sql

Question

Hello
I am writing a pl-sql which will perform SCD type 1.
The Type 1 methodology overwrites old data with new data, and therefore does not track historical data at all. This is most appropriate when correcting certain types of data errors, such as the spelling of a name. (Assuming you won't ever need to know how it used to be misspelled in the past.)
Another example would be of a database table that keeps supplier information.
Supplier_key      Supplier_Name      Supplier_State
001      Phlogistical Supply Company      CA
so hence I created two tables
create table ssn_load1
( ssn number(10,0),
credit_score number(6,0));
create table ssn_load2
( ssn number(10,0),
credit_score number(6,0));
and the target table
create table ssn_target
( sq_id number(8,0) primary key,
ssn number(10,0),
credit_score number(6,0));
since I want sq_id as auto incremented,I have created a following trigger
CREATE SEQUENCE test_sequence
START WITH 1
INCREMENT BY 1;
CREATE OR REPLACE TRIGGER test_trigger
BEFORE INSERT
ON ssn_target
REFERENCING NEW AS NEW
FOR EACH ROW
BEGIN
SELECT test_sequence.nextval INTO :NEW.SQ_ID FROM dual;
END;
Now inoder to perform type 1 I have followed a following thing
YOu have source table
tbl1(col1, col2, col3) - where col1 is the key and (col2, col3) are the attributes
target table
tbl2(col21, col22) - where (col21, col21) are the attributes
do this join for change data capture
select <col list>,
case when col22 is null and col23 is null then 'NEW'
when col2 = col22 and col3 = col23 then 'NO CHANGE'
else 'MODIFIED' end
from
tbl1 LEFT OUTER JOIN tbl2
ON tbl1.col1 = tbl2.col21
following is my pl-sql ,but I dont know how to write insert update statement in the switch case.
declare
cursor ssn1
is select from ssn_load1;*
for row in ssn1 loop
select s2.ssn,s2.credit_score from ssn_load2 s2 left outer join  ssn_load1 s1 on s1.ssn=s2.ssn;
*     SWITCH (ssn)*
*     DO*
CASE 'Insert':if s2.ssn!=s1.ssn
Insert into ssn_target(ssn,credit_score)values();
CASE 'No Change':
CASE 'Modify':Update ssn_target set
DEFAULT:
DO END;
end loop;
END;
please help me how to proceed from here
will be waiting for reply
Thank You!!

Answer 1

Isn't this a MERGE?
In the outer join approach, it might be simpler to do the join in the cursor and keep the PL/SQL simple. I didn't really understand your three-table scenario though.