Delete thousands of cron jobs

I discovered that I have 29,000 cron jobs in my WordPress database from deactivated and deleted plugins. I have tried a number of optimizer plugins but the huge number of cron jobs means I can't delete them using plugins.

I also tried this in my functions.php without success:

add_action("init", "clear_crons_left");
function clear_crons_left() {
    wp_clear_scheduled_hook("cron_name");
}

Is there any SQL command I can use in phpmyadmin to search by cron hook and remove them?