databse store data with underscores
There are no direct technical issue with using an underscore in the name. In fact, I do it quite often and find it helpful. Ruby even auto generate underscores in column names and SQL Servers own system objects use underscores too.
In general, it is a good idea to have some naming convention that you stick to in the database, and if that includes underscores, no big deal.
Any character can be used in the name, if you put square brackets or quotes around the name when referring to it. I try to avoid spaces though, since it makes things harder to read.
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