Avoiding Duplicate Data Before Update syntax for a Table

Question

Dear All,
CREATE TABLE TABLENAME
ID NUMBER,
COUNTRY VARCHAR2(10),
STATE VARCHAR2(10),
JOB VARCHAR2(10),
RNO VARCHAR2(10)
The rows looks like this
ID | COUNTRY | STATE | JOB | RNO
1 | India | Delhi | Abc | IndDel000001
2 | USA | NewYork | Def | USANew000001
3 | Japan | Tokyo | Ghi | JapTok000001
4 | India | Delhi | Abc | IndDel000002
5 | USA | LosAngeles | Def | USALos000001
6 | India | Delhi | Ghi | IndDel000003
The format goes this way to update RNO Field
select LPAD(NVL(MAX(CAST(SUBSTR(RNO,7) AS INT))+1,1),6,'0') AS INC_NO FROM TableName
where SUBSTR(RNO,1,3) = VAR_COUNTRY
AND SUBSTR(RNO,4,3) = VAR_STATE
SUPPOSE VAR_COUNTRY ='IND'
VAR_STATE ='DEL'
THE OUTPUT SHOULD BE INDDEL000004
UPDATE TABLENAME
SET RNO = VAR_COUNTRY || VAR_STATE || INC_NO
WHERE ID = IDNO;
COMMIT;
Records get inserted into this table from various users accross the world
The Higlighted field is RNo which is used during updation from different users at certian vaildation rules defined
During this time it is possible that 2 or more users get the same INC_NO
for a specfic VAR_COUNTRY and VAR_STATE
so what happens RNO fiellds get duplicated which should not be the case
The RNO field should bu unique
we cannot index the Field RNO since this field is empty while inserting records in TableName Table so the field is null and gets updated later at a certain stage
Plse help me
Best Regards
Edited by: user10996371 on Nov 2, 2009 8:49 PM

Answer 1

1) You are looking for serial numbers.
2) There is no other option than Sequences (To my knowledge :) )
You will have to do some ground work.
the ground work will be
1) Chalk out all the countries/states combination you have
2) create sequences for them
3) Create a function which will give you the next number for that combination
4) PLan to give corrrect privileges to users who will eb using this.
Below the code that i tested.
CREATE SEQUENCE ind_del INCREMENT BY 1;
CREATE SEQUENCE usa_new INCREMENT BY 1;
CREATE SEQUENCE jap_tok INCREMENT BY 1;
CREATE OR REPLACE FUNCTION nxt_num (cnt_name VARCHAR2,state_name VARCHAR2)
RETURN NUMBER IS
sql_stmt VARCHAR2(500);
next_num NUMBER(10);
BEGIN
EXECUTE IMMEDIATE 'select '||cnt_name||'_'||state_name||'.nextval from dual'INTO next_num;
RETURN next_num;
END nxt_num;
select '&cnt_name'||'&state_name'||lpad(nxt_num('&cnt_name','&state_name'),6,0) FROM dual;
You may have to benchmark it for performance
Cheers!!!
Bhushan
Edited by: Buga on Nov 3, 2009 10:47 AM