Update duplicate latitude values by iteratively increasing margin - sql

Question

I have lat and long columns in an Oracle database table stored as regular numbers.
Some of which are duplicates. I'd like a way to add a very small margin to either column to eliminate duplication. Problem is, for each identical pair the number of duplicate records might vary. In this case I have to adjust the margin I add iteratively for each pair.
example:
ID | LAT | LONG
==================
1 | 1 | 1
2 | 1 | 1
3 | 1 | 1
in this case, I'd like to add a margin of .0003 to either column to eliminate the duplication, but I can't just blindly add that .0003 to IDs 2 and 3 because they would still be duplicates, so I have to do original_value + (margin*i) for i in (0...number of duplicate rows)
so I'd like to end up with something like this:
ID | LAT | LONG
1 | 1 | 1
2 | 1.0003 | 1
3 | 1.0006 | 1
How do I do this in SQL? I can mimic imperative programming apparently with cursors but it does not seem to be the SQL way. Can I somehow achieve this with INSERT INTO SELECT?

Answer 1

I don't know what your exact data looks like, but suppose you have this table, called tbl:
ID LAT LON
---------- ---------- ----------
1 20 25
2 30 33
3 30 33
4 55 60
5 55 60
6 55 60
You could run the following:
select id,
case when rn > 1 then lat+rn-1 else lat end as lat,
lon
from(
select t.*,
row_number() over(partition by lat, lon order by id) as rn
from tbl t
) x;
To get:
ID LAT LON
---------- ---------- ----------
1 20 25
2 30 33
3 31 33
4 55 60
5 56 60
6 57 60
Notice how IDs 2 and 3 were dups, and IDs 4, 5, and 6, were dups. They are no longer exact dups because the lat value has increased, sequentially, to make the rows not duplicates. They go up by one for each next duplicate.
Fiddle: http://sqlfiddle.com/#!4/ef959/1/0
Edit (based on your edit)
select id,
case when rn > .0003 then lat+rn-.0003 else lat end as lat,
lon
from(
select t.*,
row_number() over(partition by lat, lon order by id)*.0003 as rn
from tbl t
) x;
The above will ascend by .0003 rather than 1.
See new fiddle here: http://sqlfiddle.com/#!4/21506/6/0