MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6
The date and time data types for representing temporal values
are DATE,
TIME,
DATETIME,
TIMESTAMP, and
YEAR.
For the DATE and
DATETIME range descriptions,
“supported” means that although earlier values
might work, there is no guarantee.
MySQL permits fractional seconds for
TIME,
DATETIME, and
TIMESTAMP values, with up to
microseconds (6 digits) precision. To define a column that
includes a fractional seconds part, use the syntax
,
where type_name(fsp)type_name is
TIME,
DATETIME, or
TIMESTAMP, and
fsp is the fractional seconds
precision. For example:
CREATE TABLE t1 (t TIME(3), dt DATETIME(6), ts TIMESTAMP(0));
The fsp value, if given, must be in
the range 0 to 6. A value of 0 signifies that there is no
fractional part. If omitted, the default precision is 0. (This
differs from the standard SQL default of 6, for compatibility
with previous MySQL versions.)
Any TIMESTAMP or
DATETIME column in a table can
have automatic initialization and updating properties; see
Section 11.2.6, “Automatic Initialization and Updating for TIMESTAMP and DATETIME”.
A date. The supported range is
'1000-01-01' to
'9999-12-31'. MySQL displays
DATE values in
'
format, but permits assignment of values to
YYYY-MM-DD'DATE columns using either
strings or numbers.
A date and time combination. The supported range is
'1000-01-01 00:00:00.000000' to
'9999-12-31 23:59:59.499999'. MySQL
displays DATETIME values in
'
format, but permits assignment of values to
YYYY-MM-DD
hh:mm:ss[.fraction]'DATETIME columns using either
strings or numbers.
An optional fsp value in the
range from 0 to 6 may be given to specify fractional seconds
precision. A value of 0 signifies that there is no
fractional part. If omitted, the default precision is 0.
Automatic initialization and updating to the current date
and time for DATETIME columns
can be specified using DEFAULT and
ON UPDATE column definition clauses, as
described in Section 11.2.6, “Automatic Initialization and Updating for TIMESTAMP and DATETIME”.
A timestamp. The range is '1970-01-01
00:00:01.000000' UTC to '2038-01-19
03:14:07.499999' UTC.
TIMESTAMP values are stored
as the number of seconds since the epoch
('1970-01-01 00:00:00' UTC). A
TIMESTAMP cannot represent
the value '1970-01-01 00:00:00' because
that is equivalent to 0 seconds from the epoch and the value
0 is reserved for representing '0000-00-00
00:00:00', the “zero”
TIMESTAMP value.
An optional fsp value in the
range from 0 to 6 may be given to specify fractional seconds
precision. A value of 0 signifies that there is no
fractional part. If omitted, the default precision is 0.
The way the server handles TIMESTAMP
definitions depends on the value of the
explicit_defaults_for_timestamp
system variable (see
Section 5.1.7, “Server System Variables”).
If
explicit_defaults_for_timestamp
is enabled, there is no automatic assignment of the
DEFAULT CURRENT_TIMESTAMP or ON
UPDATE CURRENT_TIMESTAMP attributes to any
TIMESTAMP column. They must
be included explicitly in the column definition. Also, any
TIMESTAMP not explicitly
declared as NOT NULL permits
NULL values.
If
explicit_defaults_for_timestamp
is disabled, the server handles TIMESTAMP
as follows:
Unless specified otherwise, the first
TIMESTAMP column in a table
is defined to be automatically set to the date and time of
the most recent modification if not explicitly assigned a
value. This makes TIMESTAMP
useful for recording the timestamp of an
INSERT or
UPDATE operation. You can
also set any TIMESTAMP column
to the current date and time by assigning it a
NULL value, unless it has been defined
with the NULL attribute to permit
NULL values.
Automatic initialization and updating to the current date
and time can be specified using DEFAULT
CURRENT_TIMESTAMP and ON UPDATE
CURRENT_TIMESTAMP column definition clauses. By
default, the first TIMESTAMP
column has these properties, as previously noted. However,
any TIMESTAMP column in a
table can be defined to have these properties.
A time. The range is '-838:59:59.000000'
to '838:59:59.000000'. MySQL displays
TIME values in
'
format, but permits assignment of values to
hh:mm:ss[.fraction]'TIME columns using either
strings or numbers.
An optional fsp value in the
range from 0 to 6 may be given to specify fractional seconds
precision. A value of 0 signifies that there is no
fractional part. If omitted, the default precision is 0.
A year in 4-digit format. MySQL displays
YEAR values in
YYYY format, but permits
assignment of values to YEAR
columns using either strings or numbers. Values display as
1901 to 2155, or
0000.
The YEAR(2) data type is
deprecated and support for it is removed in MySQL 5.7.5.
To convert 2-digit YEAR(2)
columns to 4-digit YEAR
columns, see Section 11.2.5, “2-Digit YEAR(2) Limitations and Migrating to 4-Digit YEAR”.
For additional information about
YEAR display format and
interpretation of input values, see Section 11.2.4, “The YEAR Type”.
The SUM() and
AVG() aggregate functions do not
work with temporal values. (They convert the values to numbers,
losing everything after the first nonnumeric character.) To work
around this problem, convert to numeric units, perform the
aggregate operation, and convert back to a temporal value.
Examples:
SELECT SEC_TO_TIME(SUM(TIME_TO_SEC(time_col))) FROMtbl_name; SELECT FROM_DAYS(SUM(TO_DAYS(date_col))) FROMtbl_name;
The MySQL server can be run with the
MAXDB SQL mode enabled. In
this case, TIMESTAMP is
identical with DATETIME. If
this mode is enabled at the time that a table is created,
TIMESTAMP columns are created
as DATETIME columns. As a
result, such columns use
DATETIME display format, have
the same range of values, and there is no automatic
initialization or updating to the current date and time. See
Section 5.1.10, “Server SQL Modes”.
As of MySQL 5.7.22, MAXDB is
deprecated; expect it to removed in a future version of MySQL.