vaultwarden/migrations/2018-07-11-181453_create_u2f_twofactor/up.sql

CREATE TABLE twofactor (
  uuid      VARCHAR(40) NOT NULL PRIMARY KEY,
  user_uuid VARCHAR(40) NOT NULL REFERENCES users (uuid),
  atype      INTEGER  NOT NULL,
  enabled   BOOLEAN  NOT NULL,
  data      TEXT     NOT NULL,

  UNIQUE (user_uuid, atype)
);


INSERT INTO twofactor (uuid, user_uuid, atype, enabled, data) 
SELECT UUID(), uuid, 0, 1, u.totp_secret FROM users u where u.totp_secret IS NOT NULL;

UPDATE users SET totp_secret = NULL; -- Instead of recreating the table, just leave the columns empty