This almost worked for me.
I had errors saying username already in use.
Had to
mysql -u root -p
then
use mynextclouddb
next,
DROP TABLE oc_accounts, oc_activity, oc_activity_mq, oc_addressbookchanges, oc_addressbooks, oc_admin_sections, oc_admin_settings, oc_appconfig, oc_authtoken, oc_bruteforce_attempts, oc_calendarchanges, oc_calendarobjects, oc_calendarobjects_props, oc_calendars, oc_calendarsubscriptions, oc_cards, oc_cards_properties, oc_comments, oc_comments_read_markers, oc_credentials, oc_dav_shares, oc_federated_reshares, oc_file_locks, oc_filecache, oc_files_trash, oc_flow_checks, oc_flow_operations, oc_group_admin, oc_group_user, oc_groups, oc_jobs, oc_mimetypes, oc_mounts, oc_notifications, oc_notifications_pushtokens, oc_oauth2_access_tokens, oc_oauth2_clients, oc_preferences, oc_privatedata, oc_properties, oc_schedulingobjects, oc_share, oc_share_external, oc_storages, oc_systemtag, oc_systemtag_group, oc_systemtag_object_mapping, oc_trusted_servers, oc_twofactor_backupcodes, oc_users, oc_vcategory, oc_vcategory_to_object;
BINGO… Back in from the begining !