What's the significance of # in SQL?

I have the following code to create an object type in Oracle (PL??)

CREATE OR REPLACE TYPE STAFF开发者_如何学Go_T as OBJECT(Staff_ID# NUMBER, Person PERSON_T); \

I'd like to know what is the significance of the # appended to the Staff_ID variable in the declaration?

No special meaning.

Oracle allows using $, _ and # in identifiers, just like any other alphanumeric characters, but the identifier should begin with an alpha character (a letter).

That's part of the column name Staff_ID#. The pound sign is an allowable part of an identifier (table/column name) in PL/SQL. See here

Whoever wrote the code probably didn't mean anything special by #.

But # apparently means something to Oracle, although I don't know what. From the SQL Language Reference:

Oracle strongly discourages you from using $ and # in nonquoted identifiers.

Here are some guesses for what the warning is about:

• it's related to a really old bug (the warning goes back to at least Oracle 7)
• Oracle plans to do something with it in a future verison
• that character isn't available on all keyboards, character sets, or platforms that Oracle supports

The data dictionary uses the number sign a lot, and as far as I can tell it works just fine for user objects. But just to be safe you might want to remove it.