Oracle 5.0, Справочное руководство

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Numeric Types
834
•
ENUM('value1','value2',...) [CHARACTER SET charset_name] [COLLATE
collation_name]
An enumeration. A string object that can have only one value, chosen from the list of values
'value1'
,
'value2'
,
...
,
NULL
or the special
''
error value.
ENUM
values are represented
internally as integers.
An
ENUM
column can have a maximum of 65,535 distinct elements. (The practical limit is less than
3000.) A table can have no more than 255 unique element list definitions among its
ENUM
and
SET
columns considered as a group. For more information on these limits, see Section E.7.5, “Limits
Imposed by
.frm
File Structure” .
•
SET('value1','value2',...) [CHARACTER SET charset_name] [COLLATE
collation_name]
A set. A string object that can have zero or more values, each of which must be chosen from the list
of values
'value1'
,
'value2'
,
... SET
values are represented internally as integers.
A
SET
column can have a maximum of 64 distinct members. A table can have no more than 255
unique element list definitions among its
ENUM
and
SET
columns considered as a group. For more
information on this limit, see Section E.7.5, “Limits Imposed by
.frm
File Structure” .
11.1.4. Numeric Types
MySQL supports all standard SQL numeric data types. These types include the exact numeric data
types (
INTEGER
,
SMALLINT
,
DECIMAL
, and
NUMERIC
), as well as the approximate numeric data
types (
FLOAT
,
REAL
, and
DOUBLE PRECISION
). The keyword
INT
is a synonym for
INTEGER
, and
the keywords
DEC
and
FIXED
are synonyms for
DECIMAL
. MySQL treats
DOUBLE
as a synonym for
DOUBLE PRECISION
(a nonstandard extension). MySQL also treats
REAL
as a synonym for
DOUBLE
PRECISION
(a nonstandard variation), unless the
REAL_AS_FLOAT
[539] SQL mode is enabled.
As of MySQL 5.0.3, a
BIT
data type is available for storing bit-field values. (Before 5.0.3, MySQL
interprets
BIT
as
TINYINT(1)
.) In MySQL 5.0.3,
BIT
is supported only for
MyISAM
. MySQL 5.0.5
extends
BIT
support to
MEMORY
,
InnoDB
,
BDB
, and
NDBCLUSTER
.
For information about how MySQL handles assignment of out-of-range values to columns and overflow
during expression evaluation, see
Section 11.1.4.6, “Out-of-Range and Overflow Handling” .
For information about numeric type storage requirements, see Section 11.2, “Data Type Storage
Requirements” .
The data type used for the result of a calculation on numeric operands depends on the types of the
operands and the operations performed on them. For more information, see
Section 12.6.1, “Arithmetic
Operators” .
11.1.4.1. Integer Types (Exact Value) -
INTEGER
,
INT
,
SMALLINT
,
TINYINT
,
MEDIUMINT
,
BIGINT
MySQL supports the SQL standard integer types
INTEGER
(or
INT
) and
SMALLINT
. As an extension
to the standard, MySQL also supports the integer types
TINYINT
,
MEDIUMINT
, and
BIGINT
. The
following table shows the required storage and range for each integer type.
Type Storage Minimum Value Maximum Value
(Bytes) (Signed/Unsigned) Signed/Unsigned)
TINYINT
1
-128 127
0 255
SMALLINT
2
-32768 32767