Approximate numeric datatypes store
floating-point numbers like fractions where an approximation must be
made. For instance, an accurate number, per se, cannot be stored for
1/3, because the decimal point for 3 continues on endlessly. Table A-2 lists approximate numeric datatypes. There are
synonyms for a few of these types. DOUBLE
and
REAL
are synonyms for DOUBLE
PRECISION
. However, if the SQL mode for the server has the
REAL_AS_FLOAT
option enabled,
REAL
is a synonym for FLOAT
.
For FLOAT
, a level of precision may be specified.
It may be from 0 to 24 for single-precision floating-point numbers
and from 25 to 53 for double-precision floating-point numbers. If a
precision isn’t given with FLOAT
,
a single-precision floating point is assumed. With
DOUBLE
, if UNSIGNED
is
specified, negative values are not allowed.
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