Renaming duplicates per group in sql - mysql

Question

I want to write a query that will update duplicates per group:
INPUT
+-------+-------+
| group | name |
+-------+-------+
| 1 | name1 |
| 1 | name1 |
| 1 | name1 |
| 1 | name2 |
| 2 | name1 |
| 2 | name1 |
| 3 | name1 |
| 3 | name2 |
+-------+-------+
OUTPUT
+-------+----------------+
| group | name |
+-------+----------------+
| 1 | name1 |
| 1 | name1 - Copy 1 |
| 1 | name1 - Copy 2 |
| 1 | name2 |
| 2 | name1 |
| 2 | name1 - Copy 1 |
| 3 | name1 |
| 3 | name2 |
+-------+----------------+
There is something like that here Renaming the duplicate data in sql but my problem is how to deal with groups.
It is not so important how to name this duplicates but it will be cool if I can do it as specified in my example.

Answer 1

If you have a primary key id column, then try this:
update (
select `group`, name, min(id) as min_id
from test
group by `group`, name
) x
join test t using (`group`, name)
set t.name =
case when t.id <> x.min_id
then concat(t.name, ' - Copy ', t.id - x.min_id)
else t.name
end
;
Demo: http://rextester.com/AWEX77086
Here is another way, which is probably slower, but will guarantee consecutive copy numbers.
update (
select l.id, count(*) as copy_nr
from test l
join test r
on r.group = l.group
and r.name = l.name
and r.id < l.id
group by l.id
) x
join test t using (id)
set t.name = concat(t.name, ' - Copy ', x.copy_nr);
Demo: http://rextester.com/NWSF57017

Answer 2

Try the below, replace Groups, with Group.
Ok, I was pointed out that this is a MySQL question, so the below wont work for MySQL, but only for t-sql.
SELECT Groups,
CASE WHEN Duplicate > 1
THEN Name + ' - Copy ' + CONVERT(VARCHAR(10), Duplicate)
ELSE Name
END AS Name
FROM
(
SELECT Groups,
Name,
ROW_NUMBER() OVER(PARTITION BY Name, Groups ORDER BY Name ) As Duplicate
FROM TableName
) AS Data
ORDER BY Groups

Answer 3

This is untested, but you can similate the LAG function seen in many other RDBMS' with variables (more info here).
The idea is you store the group and name fields and compare against them before updating them.
SET #RowNumber = 0;
SET #PreviousGroup = NULL;
SET #PreviousName = NULL;
SELECT
#PreviousGroup AS PreviousGroup,
#PreviousName AS PreviousName,
CASE
WHEN #PreviousGroup = `group` AND #PreviousName = `name` THEN (#RowNumber := #RowNumber + 1)
ELSE #RowNumber := 0
END AS `Counter`,
CASE
WHEN #PreviousGroup = `group` AND #PreviousName = `name` THEN CONCAT(`name`,'- Copy ',#RowNumber)
ELSE `name`
END AS `Name`,
#PreviousGroup := `group` AS RawGroup,
#PreviousName := `name` AS RawName
FROM
tbl1
ORDER BY
`group` ASC,
`name` ASC;

Answer 4

You can do this using variables. I would recommend:
set #i = 0;
set #gn := '';
update t
set name = concat_ws(' - Copy ', name,
nullif(if(#gn = concat_ws(':', group, name), #i := #i + 1,
if(#gn := concat_ws(':', group, name), #i := 1, #i := 1)
), 0)
order by t.group, name;