PostgreSQL has allowed me to name a column "campaign_$". I like the name because it's short and to the point, and other potential names like "campaign_receipts" seem longer and less clear.
BUT, I wonder if I'll eventually regret putting a $ symbol in a column name, either in PHP or in some other distant part of the architecture. Should I just stick to letters and underscores?
Thanks!
You probably won't regret, but I still wouldn't recommend it.
What happens when you expand into Europe?
Also, it will look strange and confusing to new developers.
I think it is bad practice to put special characters into a column name. Just spell out the word like campaign_money or campaign_funds and then the issue of internationalization or other possible issues become a thing of the past.
There's a VERY strong convention that tables and columns are named using only letters, numbers, and (possibly) underscores, so I would consider this poor style. Beyond the i18n concerns that other posters mention, there are probably a very large number of tools that expect table and column names following this convention.
It should be fine, however it may cause you more problems down the line when you want to export the data to another system, things like that.
It's good to get into the habbit of naming columns/variables etc with no special characters, as usually they are more trouble than they are worth.
In addition to the other excellent reasons I'll also mention that "$" in my mind is not clear at all. Does that mean campaign expenses? Campaign savings? Campaign values?
I wouldn't use it.
The "$" might not be valid in future databases you use (at some point you might migrate away from PostgreSQL to something else) and it also might pose problems at the application level if you do anything that maps column names to object properties if your programming language doesn't allow method names to have "$" in them.
Just my suggestion.