The SQL-92 standard supports a variety of built-in domain types:
char(n) (or character(n)): fixed-length character string,
with user-specified length.
varchar(n) (or character varying): variable-length
character string, with user-specified maximum length.
int or integer: an integer (length is machine-dependent).
smallint: a small integer (length is machine-dependent).
numeric(p, d): a fixed-point number with user-specified
precision, consists of p digits (plus a sign) and d of p digits
are to the right of the decimal point.
E.g., numeric(3, 1) allows 44.5 to be stored exactly but not 444.5.
real or double precision: floating-point or double-precision
floating-point numbers, with machine-dependent precision.
float(n): floating-point, with user-specified precision of at
least n digits.
date: a calendar date, containing four digit year, month,
and day of the month.
time: the time of the day in hours, minutes, and seconds.
SQL-92 allows arithmetic and comparison operations on various numeric domains,
including, interval and cast (type coercion) such as
transforming between smallint and int.
It considers strings with different length are compatible types as well.
