Run the below query if you wish to bulk delete all the pending comments in wordpress. To run the query select SQL, paste the query and click GO.

DELETE from wp_comments WHERE comment_approved = ‘0’

Run the following query if you wish to bulk delete all approved comments in wordpress
DELETE from wp_comments WHERE comment_approved = ‘1’

Run the following query if you wish to bulk delete all spam comments in wordpress
DELETE from wp_comments WHERE comment_approved = ‘spam’

Run the below query if you wish to bulk delete all the trash comments in wordpress
DELETE from wp_comments WHERE comment_approved = ‘trash’