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How to delete duplicate records?

Discussion in 'Databases' started by nsharony, Jun 16, 2017.

  1. #1

    I've been struggling with this problem and hopefully someone could point me in the right direction.

    I have a table like so:
    Each row represents a user who has a mobile device with an install game.
    Row 1 says that user 1 has device abc and with game 1 installed on it.
    The same user has game 2 installed on the same device (as seen by row 2)

    What I need to do is to identify all the duplicate and to delete them so that at the end,
    any device that has more than 1 game installed by the same user will be delete.
    This query gives me the breakdown of the number of duplicates per user and game:
    select game, user, count(*) from `data` group by 1,2
    Code (markup):
    This gives this result:
    This means that user 1 has game 1 installed on two devices and also game 2 installed on two devices.

    What I would like to do is to delete all the records that cause the count(*) in the group by to return any value greater than 1.
    The end result should be being left with just these records:
    Does anyone know what is the correct way of doing this?
    nsharony, Jun 16, 2017 IP
  2. PoPSiCLe

    PoPSiCLe Illustrious Member

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    I think DISTINCT can do this for you - SELECT DISTINCT user, COUNT(*) FROM table or similar.
    PoPSiCLe, Jun 17, 2017 IP
  3. K Padmapriya

    K Padmapriya Member

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    For deleting a record ,
    SQL>DELETEFROM table_name A WHERE ROWID> ( 2 SELECT min(rowid) FROM table_name B 3 WHERE A.Key_values=B.key_values);
    K Padmapriya, Nov 6, 2017 IP