MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6

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`

.