CODEWITHSUNDEEP
sqlsqlitedb-browser-sqlite
Alex Rebell
Alex Rebell

Reputation: 374

Change duplicate value in a column

Can you please tell me what SQL query can I use to change duplicates in one column of my table? I found these duplicates:

SELECT Model, count(*) FROM Devices GROUP BY model HAVING count(*) > 1;

I was looking for information on exactly how to change one of the duplicate values, but unfortunately I did not find a specific option for myself, and all the more information is all in abundance filled by deleting the duplicate value line, which I don't need. Not strong in SQL at all. I ask for help. Thank you so much.

Upvotes: 0

Views: 1525

Answers (3)

Alex Rebell
Alex Rebell

Reputation: 374

After the command:

SELECT Model, count (*) FROM Devices GROUP BY model HAVING count (*)> 1;

i get the result:

  • 1895 lines = NULL;
  • 3383 lines with duplicate values;
  • and all these values are 1243.

after applying your command:

update Devices set
  Model = '-'
where id not in
  (select
     min(Devices .id)
   from Devices 
   group by Devices.Model)

i got 4035 lines changed. if you count, it turns out, (3383 + 1895) = 5278 - 1243 = 4035 and it seems like everything fits together, the result suits, it works.

Upvotes: 0

Popeye
Popeye

Reputation: 35930

use exists as follows:

update d 
   set Model = '-'
  from Devices d
where exists (select 1 from device dd where dd.model = d.model and dd.id > d.id)

Upvotes: 0

Barbaros Özhan
Barbaros Özhan

Reputation: 65408

You can easily use a Window Functions such as ROW_NUMBER() with partitioning option in order to group by Model column to eliminate the duplicates, and then pick the first rows(rn=1) returning from the subquery such as

WITH d AS
(
 SELECT *, ROW_NUMBER() OVER (PARTITION BY Model) AS rn
   FROM Devices 
)
SELECT ID, Model -- , and the other columns
  FROM d
 WHERE rn = 1

Demo

Upvotes: 1

Related Questions