SQL & PL/SQL :: Find Query To Create Gap In Continuous Series?

I need to find a query to create a gap in continuous series. So that i can fill this gap with a new record.

Attached here is the test sql.

Sample Data is

test@orcl>select * from sales_mst;

NO VDATE T
---------- --------- -
1245 07-JAN-13 N
1246 07-JAN-13 N
1247 07-JAN-13 R
1248 07-JAN-13 N

[code]...

10 rows selected.

test@orcl>select * from sales_dtl;

NO CODE QTY RATE
---------- ---------- ---------- ----------
1245 11 60 600
1246 12 55 450
1246 11 45 600
1247 13 50 250
1247 11 60 600
1248 11 45 600
1249 12 55 450

[code]...

16 rows selected.

Required Out Put

test@orcl>select * from sales_mst;

NO VDATE T
---------- --------- -
1245 07-JAN-13 N
1246 07-JAN-13 N
1247 07-JAN-13 R
1248 07-JAN-13 N
1251 08-JAN-13 N
1250 08-JAN-13 R
1253 08-JAN-13 N
1252 09-JAN-13 R
1254 09-JAN-13 N
1255 09-JAN-13 N

10 rows selected.

test@orcl>select * from sales_dtl;

NO CODE QTY RATE
---------- ---------- ---------- ----------
1245 11 60 600
1246 12 55 450
1246 11 45 600
1247 13 50 250
1247 11 60 600
1248 11 45 600
1251 12 55 450
1251 11 45 600

[code]...

16 rows selected.

Update or move only those records which have Type 'N'. I have tried the following query but it is giving me an error.

test@orcl>ALTER TABLE
sales_dtl
DISABLE CONSTRAINT
fk_sales_dtl_no;
test@orcl>update sales_mst set no=no+1 where type='N' and vdate > '07-JAN-13';
*
ERROR at line 1:
ORA-00001: unique constraint (TEST.PK_SALES_MST_NO) violated