Question

I have a table of data which has posts, then I have a separate table of data which has deleted posts. What happens when a post is deleted is that it’s ID get’s added to the deleted table rather than removing the post entry.

What is a clean efficient way of selecting all the posts from the posts table without selecting the ones that have their ID in the deleted table

Answer 1

If you can’t change your tables, you can do a Left Join (which will join your deleted_table when possible) and then check for the id to be Null (means that no row has been found).

Select everything_you_need
From post_table p
Left Join delete_table d On ( d.id = p.id )
Where d.id Is Null;

Make sure to have indexes on both id-columns for best performance.