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21.1 Types of Numeric Values
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The scope of precision math for exact-value operations includes the
exact-value data types (`DECIMAL' and integer types) and exact-value
numeric literals. Approximate-value data types and numeric literals
still 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 need not be both exact-value or both
approximate-value. 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'.
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