How to use the physical location of rows (ROWID) in a DELETE statement

database, postgresql, rowid, sql

Solution

On PostgreSQL the physical location of the row is called CTID.

So if you want to view it use a QUERY like this:

SELECT CTID FROM table_name

To use it on a DELETE statement to remove the duplicated records use it like this:

DELETE FROM table_name WHERE CTID NOT IN (
  SELECT RECID FROM 
    (SELECT MIN(CTID) AS RECID, other_columns 
      FROM table_name GROUP BY other_columns) 
  a);

Remember that table_name is the desired table and other_columns are the columns that you want to use to filter that.

Ie:

DELETE FROM user_department WHERE CTID NOT IN (
  SELECT RECID FROM 
    (SELECT MIN(CTID) AS RECID, ud.user_id, ud.department_id
      FROM user_department ud GROUP BY ud.user_id, ud.department_id) 
  a);

Problem

I have a table that has a lot of duplicated rows and no primary key. I want to remove just the duplicated records, but when I try to do this it would remove all peers. How can I find the `ROWID` from a table in Postgres?

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