MySQL 9.1 Release Notes
The scope of precision math for exact-value operations includes
the exact-value data types (integer and
DECIMAL types) and exact-value
numeric literals. Approximate-value data types and numeric
literals are handled as floating-point numbers.
Exact-value numeric literals have an integer part or fractional
part, or both. They may be signed. Examples: 1,
.2, 3.4,
-5, -6.78,
+9.10.
Approximate-value numeric literals are represented in scientific
notation with a mantissa and exponent. Either or both parts may be
signed. Examples: 1.2E3,
1.2E-3, -1.2E3,
-1.2E-3.
Two numbers that look similar may be treated differently. For
example, 2.34 is an exact-value (fixed-point)
number, whereas 2.34E0 is an approximate-value
(floating-point) number.
The DECIMAL data type is a
fixed-point type and calculations are exact. In MySQL, the
DECIMAL type has several synonyms:
NUMERIC,
DEC,
FIXED. The integer types also are
exact-value types.
The FLOAT and
DOUBLE data types are
floating-point types and calculations are approximate. In MySQL,
types that are synonymous with
FLOAT or
DOUBLE are
DOUBLE PRECISION and
REAL.