Joe Celko's SQL for Smarties, 3rd Edition

7.3. Currency and Other Unit Conversions

Currency has to be expressed in both an amount and a unit of currency. The ISO 4217 currency code gives you a standard way of identifying the unit. There are no nondecimal currency systems left on earth, but you will need to talk to the accounting department about the number of decimal places to use in computations. The rules for euros are established by the European Union, and those for U.S. dollars are part of the GAAP (Generally Accepted Accounting Practices).

CREATE TABLE InternationalMoney
( ...
currency_code CHAR(3) NOT NULL,
currency_amt DECIMAL (12,4) NOT NULL,
...);

This mixed table is not easy to work with, so it is best to create VIEWs with a single currency for each group of users. This will ...