SQL to change the id of a Paid Memberships Pro level from old_id to new_id. Please BACKUP YOUR DATABASE FIRST, make sure to change the DB table names to match your prefix, and make sure that there is not another level with

pmpro-change-level-id.sql

# change these vars
SET @old_id = 2;
SET @new_id = 1;

# change the db table prefix here
UPDATE IGNORE wp_pmpro_membership_levels SET id = @new_id WHERE id = @old_id;
UPDATE IGNORE wp_pmpro_discount_codes_levels SET level_id = @new_id WHERE level_id = @old_id;
UPDATE IGNORE wp_pmpro_membership_orders SET membership_id = @new_id WHERE membership_id = @old_id;
UPDATE IGNORE wp_pmpro_memberships_categories SET membership_id = @new_id WHERE membership_id = @old_id;
UPDATE IGNORE wp_pmpro_memberships_pages SET membership_id = @new_id WHERE membership_id = @old_id;
UPDATE IGNORE wp_pmpro_memberships_users SET membership_id = @new_id WHERE membership_id = @old_id;

This hasn't been updated in 10 years but I'm happy to report it mostly works though a few new tables were part of my installation at least.

Here's the code that I used:

SET @old_id = 1;
SET @new_id = 2;

UPDATE IGNORE wp_pmpro_membership_levelmeta SET pmpro_membership_level_id = @new_id WHERE pmpro_membership_level_id = @old_id;
UPDATE IGNORE wp_pmpro_membership_ordermeta SET pmpro_membership_order_id = @new_id WHERE pmpro_membership_order_id = @old_id;
UPDATE IGNORE wp_pmpro_membership_levels SET id = @new_id WHERE id = @old_id;
UPDATE IGNORE wp_pmpro_memberships_categories SET membership_id = @new_id WHERE membership_id = @old_id;
UPDATE IGNORE wp_pmpro_membership_orders SET membership_id = @new_id WHERE membership_id = @old_id;
UPDATE IGNORE wp_pmpro_memberships_pages SET membership_id = @new_id WHERE membership_id = @old_id;
UPDATE IGNORE wp_pmpro_memberships_users SET membership_id = @new_id WHERE membership_id = @old_id;