Do underscores in a MySQL table names cause issues?

Question

Do underscores in table names affect performance or cause issues on some platforms?

For example, user_profiles

Would it be better to use user

Answer 1

You should avoid it. Although it is a permitted character in MySQL documentation, it appears it might cause trouble. For example, in MySQL 5.0 & 5.1 (and may be later versions), the query cache is never hit for queries involving a table name containing an underscore.