mysqlgroup-concat

How remove rows by id, got by group_concat

I want to remove some rows from table.

First, i tried to use subquery, but I can't remove data from table, when use the same table in subquery.

I tried do that in another way.

set @list_id_remove = (select group_concat(mra.media_id) from movie AS m
right join media AS mra ON m.id = mra.media_id
where m.id is null);

delete from media
where media_id IN (@list_id_remove);

But in this case query remove only 1 row. I think trouble - is that group_concat remove string and I need list of integers.

Solution

  • You seem to want to delete from media where the corresponding record doesn't exist in movie. You can do this as a single query. 

    delete from media 
    where not exists (select 1 from movie m where m.id = media.media_id);

    It does seem strange to me that the field movie.id would correspond to media.media_id, but that is how your original query is written.

    EDIT:

    As for your question, you can write the delete as:

    delete from media
    where find_in_set(media_id, @list_id_remove) > 0;