Question

I need to write a SQL script to delete users with no posts associated with them in a WordPress database. I tried this script after doing some searching:

DELETE FROM wp_users WHERE ID NOT IN (SELECT DISTINCT post_author FROM wp_105_posts)

but this deleted all the users. Can someone let me know what I am doing wrong please?

Answer 1

Seems like either none of the users made posts, or wp_105_posts.post_author doesn’t link to wp_users.ID. Are you sure wp_105_posts.post_author is a Foreign Key of wp_users.ID?

wp_105_posts should have one column that references who the user is in the wp_users table. Since your GUID Primary Key for wp_users is ID, this should be the one column you use to reference the user from your post tables. Here is a small example:

user_table
ID | name | age | email | etc.
1 | nick | 24 | [e-mail] | ..
2 | bob | 30 | [e-mail] | …
3 | sue | 35 | [e-mail] | …

a_post_table
ID (ID of post) | User_ID (ID of user) | title | date | body
……..1…………..|…1 (post by nick)…….. | help | 1/1/11
……..2…………..|…1 (post by nick)…….. | help | 3/2/11
……..3…………..|…2 (post by bob)…….. | help | 5/6/11

As you can see, the post table knows everything about the author by simply holding its ID. You can use a join query to get all user info from the post table just by knowing its ID. Using this query now

DELETE FROM user_table
WHERE ID NOT IN
(SELECT DISTINCT User_ID FROM a_post_table)

Will delete Sue, and Sue only, given the data above.
HTH