SQL - How to remove repeating values - sql

Question

My requirement is to remove the repeating values.
id name surname value
1 Vinduja Vijayan 5
3 Vinduja Vijayan 6
4 Vinduja Vijayan 7
Required output:
id name surname value
1 Vinduja Vijayan 5
3 NuLL Null 6
4 NULL NULL 7

Answer 1

This transformation should usually be applied in the application layer. It is possible to do in SQL, but not recommended, by using row_number() and case:
select id,
(case when row_number() over (partition by name, surname order by id) = 1
then name
end) as name,
(case when row_number() over (partition by name, surname order by id) = 1
then surname
end) as surname
from t
order by id;
Note that the final order by is very, very important. SQL result sets (like tables) are unordered by default. Without an explicit order by, the results could be in any order, and that would mess up your interpretation of the results.

Answer 2

DECLARE #table TABLE (
Id INT
,Name VARCHAR(20)
,Surname VARCHAR(20)
,value INT
);
INSERT into #table(ID,Name,Surname,value)
Select 1,'Vinduja','Vijayan',5
Union
Select 3,'Vinduja','Vijayan',6
Union
Select 4,'Vinduja','Vijayan',7
Select S.Id ,T.Name,T.Surname,S.value from (
Select * ,ROW_NUMBER() Over(Partition by name Order by name) [Row]
From #table)S
Left join #table T On T.Id =S.Id and S.[Row]=1

Answer 3

select
id,
case when rnk=1 then name end as name,
case when rnk=1 then surname end as surname ,
value
from
(
select
id,name,surname,value,
row_number()over(partition by name,surname order by id) as rnk
from table_name)repeatname

Answer 4

I'm not sure I understand your requirements. If you just want to display the data as described, then this won't work. But if you're trying to change the data in your table, this will do that.
DECLARE #Dupes TABLE
(
id INT
,name VARCHAR(30)
,surname VARCHAR(30)
,value INT
);
INSERT #Dupes
(
id
,name
,surname
,value
)
VALUES
(1, 'Vinduja', 'Vijayan', 5),
(3, 'Vinduja', 'Vijayan', 6),
(4, 'Vinduja', 'Vijayan', 7);
WITH cte AS
(
SELECT
ROW_NUMBER() OVER (PARTITION BY [name], surname ORDER BY id) AS RowNum
,id
,name
,surname
,value
FROM #Dupes
)
UPDATE cte
SET cte.name = NULL
,cte.surname = NULL
WHERE
cte.RowNum > 1;
SELECT *
FROM #Dupes;
--Results
+----+---------+---------+-------+
| id | name | surname | value |
+----+---------+---------+-------+
| 1 | Vinduja | Vijayan | 5 |
| 3 | NULL | NULL | 6 |
| 4 | NULL | NULL | 7 |
+----+---------+---------+-------+

Answer 5

And just for interest, using the LAG function. I assumed SQL Server.
select id,
iif(name = previous_name, null, name) name,
iif(surname = previous_surname, null, surname) surname
from (
select name, surname, id,
lag(name, 1, null) over (order by name, surname, id) previous_name,
lag(surname, 1, null) over (order by name, surname, id) previous_surname
from table_name ) a
order by a.name, a.surname, a.id