I accidentally created a bunch of tables without setting the `id` field as autoincrement, having a primary key, and making the `datetime` field unique. Doing some of these things as separate steps doesn’t work because they are dependent on each other. So I combined them all into one command.
ALTER TABLE `values_Temperature` ADD PRIMARY KEY (`id`), MODIFY `id` INTEGER NOT NULL AUTO_INCREMENT, ADD UNIQUE KEY `datetime` (`datetime`);