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> Or if your language has something specific built in, use that.

Unless your language is PostgreSQL's dialect of SQL, apparently. https://wiki.postgresql.org/wiki/Don%27t_Do_This#Don.27t_use...

It has the same issue that the other suggestion of your parent comment had: it can’t deal with fractions of cents, which is an issue you will most likely run into before you will into floating point rounding issues.

Of course for databases you should use a decimal.

> In its base unit. So cents in USD. Which can be an int64.

Note that if you use cents in the US so that everything is an integer then as long as you do not have to deal with amounts that are outside the range [-$180 trillion, $180 trillion] you can also use double. Double can exactly represent all integer numbers of cents in that range.

This may be faster than int64 on some systems, especially on systems that do not provide int64 either in hardware or in the language runtime so you'd have to do it yourself.

Not necessarily. It depends on the application.