Adding NUMERIC and DECIMAL types (#186)
`NUMERIC` and `DECIMAL` types are used for arbitrary precision exact
numbers. This has a been long in development. It's required several
rewrites and some major changes and improvements to vsql in previous
versions to lay the foundation for these types to be fully integrated as
first class citizens.
Now, number literals that contains a '.' (even if they are a whole
numbers such as `123.`) are treated as `NUMERIC` with the scale and
precision determined from the number. Arithmetic operations can result
in types that are higher in scale and precision, according to the
standard (which is very specific about all of that).
As far as I'm aware vsql is the only SQL database to treat these as
distinct types according to the standard, rather than being aliases of
the same underlying type. In a nutshell, `NUMERIC` and `DECIMAL` are
both stored as fractions, but `NUMERIC` permits any denominator within
range, whereas a `DECIMAL` must have a base 10 denominator. You can
think of `DECIMAL` as having "exactly" the precision specified (i.e good
for currency), but `NUMERIC` has "at least" the precision specified.
Meaning it's possible to `CAST` a `NUMERIC` to a higher precision and
get more decimal places (from the inherent nature of a fraction). The
docs explain this much better, with examples.
Since this does introduce new storage types, a database file version
bump is required but this likely be the last version bump before v1.0.0
is released.
Along with the two new SQL types, there are some functions that work
directly with exact numbers: `ABS`, `CEIL`, `FLOOR` and `MOD`.
SQL Standard E011-03
