I saw a post from 5 years ago stating that SQL didn't have CAST or CONVERT. It's now 2020 and:
Please add these and other popular functions ASAP. It's painful these are not in there...Thank you.
Incase this helps anyone coming to this thread, as of 2/5/2020 the version of MySQL in Domo appears to be: 5.6.28-76.1-56
Current version of MySQL available to public: 8.0.19
This way you can check what functions may or may not be available.