Spec-Zone .ru
спецификации, руководства, описания, API
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Spec-Zone .ru
спецификации, руководства, описания, API
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The DATE, DATETIME, and TIMESTAMP
types are related. This section describes their characteristics, how they are similar, and how they differ.
MySQL recognizes DATE, DATETIME, and TIMESTAMP values in several formats, described in Section
9.1.3, "Date and Time Literals". For the DATE and DATETIME
range descriptions, "supported" means that although
earlier values might work, there is no guarantee.
The DATE type is used for values with a date part but no time part. MySQL retrieves
and displays DATE values in 'YYYY-MM-DD' format. The
supported range is '1000-01-01' to '9999-12-31'.
The DATETIME type is used for values that contain both date and time parts. MySQL
retrieves and displays DATETIME values in 'YYYY-MM-DD
HH:MM:SS' format. The supported range is '1000-01-01 00:00:00' to '9999-12-31 23:59:59'.
The TIMESTAMP data type is used for values that contain both date and time parts.
TIMESTAMP has a range of '1970-01-01 00:00:01' UTC to
'2038-01-19 03:14:07' UTC.
A DATETIME or TIMESTAMP value can include a trailing
fractional seconds part in up to microseconds (6 digits) precision. In particular, as of MySQL 5.6.4, any
fractional part in a value inserted into a DATETIME or TIMESTAMP
column is stored rather than discarded. With the fractional part included, the format for these values is 'YYYY-MM-DD HH:MM:SS[.fraction]', the range for DATETIME values is '1000-01-01 00:00:00.000000' to
'9999-12-31 23:59:59.999999', and the range for TIMESTAMP values is '1970-01-01 00:00:01.000000' to
'2038-01-19 03:14:07.999999'. For information about fractional seconds support in
MySQL, see Section 11.3.6, "Fractional Seconds in Time
Values".
The TIMESTAMP and (as of MySQL 5.6.5) DATETIME data
types offer automatic initialization and updating to the current date and time. For more information, see Section 11.3.5,
"Automatic Initialization and Updating for TIMESTAMP and DATETIME".
MySQL converts TIMESTAMP values from the current time zone to UTC for storage, and
back from UTC to the current time zone for retrieval. (This does not occur for other types such as DATETIME.) By default, the current time zone for each connection is the server's
time. The time zone can be set on a per-connection basis. As long as the time zone setting remains constant, you
get back the same value you store. If you store a TIMESTAMP value, and then change
the time zone and retrieve the value, the retrieved value is different from the value you stored. This occurs
because the same time zone was not used for conversion in both directions. The current time zone is available as
the value of the time_zone
system variable. For more information, see Section 10.6, "MySQL
Server Time Zone Support".
Invalid DATE, DATETIME, or TIMESTAMP
values are converted to the "zero" value of the
appropriate type ('0000-00-00' or '0000-00-00
00:00:00').
Be aware of certain properties of date value interpretation in MySQL:
MySQL permits a "relaxed"
format for values specified as strings, in which any punctuation character may be used as the delimiter
between date parts or time parts. In some cases, this syntax can be deceiving. For example, a value such
as '10:11:12' might look like a time value because of the ":" delimiter, but
is interpreted as the year '2010-11-12' if used in a date context. The
value '10:45:15' is converted to '0000-00-00'
because '45' is not a valid month.
The server requires that month and day values be valid, and not merely in the range
1 to 12 and 1 to 31, respectively. With strict mode disabled, invalid dates such as '2004-04-31' are converted to '0000-00-00'
and a warning is generated. With strict mode enabled, invalid dates generate an error. To permit such
dates, enable ALLOW_INVALID_DATES. See Section
5.1.7, "Server SQL Modes", for more information.
MySQL does not accept TIMESTAMP values that include a
zero in the day or month column or values that are not a valid date. The sole exception to this rule is
the special "zero" value '0000-00-00
00:00:00'.
Dates containing two-digit year values are ambiguous because the century is unknown. MySQL interprets two-digit year values using these rules:
Year values in the range 00-69 are
converted to 2000-2069.
Year values in the range 70-99 are
converted to 1970-1999.
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
5.1.7, "Server SQL Modes".