Re: delete query using CTE

Le 13/03/2022 à 15:44, Roger Bos a écrit :
> Hello, trying to use CTE to remove duplicates from a table.  The DELETE
> version does not work, but the SELECT version does, so I am not
> understanding what the problem is.  Any suggestions on how to fix it?
>
> Here is my query:
>
> WITH cte AS
> ( SELECT *, ROW_NUMBER() OVER ( PARTITION BY ticker, date ORDER BY
> ticker, date) my_row_num FROM price_old)
> DELETE FROM cte WHERE my_row_num > 1;
>
> I get the following error:
>
> ERROR: relation "cte" does not exist LINE 3: DELETE FROM cte WHERE
> my_row_num > 1;
>
> But when I run change the query to a select query it runs fine (in that
> it returns all the duplicate rows). For example:
>
> WITH cte AS
> ( SELECT *, ROW_NUMBER() OVER ( PARTITION BY ticker, date ORDER BY
> ticker, date) my_row_num FROM price_old)
> SELECT * FROM cte WHERE my_row_num > 1;
>
> Sample output:
>
> "US000000094541" "AAC" "2022-03-08 00:00:00-05" 9.75 9.76 9.75 9.75
> 100215 9.75 9.76 9.75 9.75 100215 0 1 2
> "US000000094541" "AAC" "2022-03-09 00:00:00-05" 9.75 9.76 9.75 9.76
> 111334 9.75 9.76 9.75 9.76 111334 0 1 2
> "US000000009823" "AAC" "2022-03-10 00:00:00-05" 9.75 9.76 9.74 9.74
> 170474 9.75 9.76 9.74 9.74 170474 0 1 2
> "US000000090393" "ABCL" "2022-03-08 00:00:00-05" 8.19 8.545 7.81 8.22
> 1984348 8.19 8.545 7.81 8.22 1984348 0 1 2
>
> Thanks,
> Roger
>

As Michael Lewis says, you can't use delete from cte but you can build
your request to do the work with something like (example from you
original request) :

WITH cte AS
( SELECT *
, ROW_NUMBER() OVER (PARTITION BY a ORDER BY b) my_row_num
, ctid -- or pk or other unique identifier if exists
FROM price_old
)
DELETE FROM tmp24
WHERE ctid IN (SELECT ctid FROM cte WHERE my_row_num = 1);

Benj