Before MySQL 5.6.4, the instances are limited in which a fractional seconds part is permitted in temporal values. A trailing fractional part is permissible in contexts such as literal values, and in the arguments to or return values from some temporal functions. Example:
mysql> SELECT MICROSECOND('2010-12-10 14:12:09.019473');
+-------------------------------------------+
| MICROSECOND('2010-12-10 14:12:09.019473') |
+-------------------------------------------+
| 19473 |
+-------------------------------------------+
However, when MySQL stores a value into a column of any temporal data type, it discards any fractional part and does not store it.
MySQL 5.6.4 and up expands fractional seconds support 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
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));
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.)
Inserting a TIME,
DATE, or
TIMESTAMP value with a
fractional seconds part into a column of the same type but
having fewer fractional digits results in rounding, as shown
in this example:
mysql>CREATE TABLE fractest( c1 TIME(2), c2 DATETIME(2), c3 TIMESTAMP(2) );Query OK, 0 rows affected (0.33 sec) mysql>INSERT INTO fractest VALUES>('17:51:04.777', '2014-09-08 17:51:04.777', '2014-09-08 17:51:04.777');Query OK, 1 row affected (0.03 sec) mysql>SELECT * FROM fractest;+-------------+------------------------+------------------------+ | c1 | c2 | c3 | +-------------+------------------------+------------------------+ | 17:51:04.78 | 2014-09-08 17:51:04.78 | 2014-09-08 17:51:04.78 | +-------------+------------------------+------------------------+ 1 row in set (0.00 sec)
No warning or error is given when such rounding occurs. This
behavior follows the SQL standard, and is not affected by
the server's sql_mode
setting.
Functions that take temporal arguments accept values with
fractional seconds. Return values from temporal functions
include fractional seconds as appropriate. For example,
NOW() with no argument
returns the current date and time with no fractional part,
but takes an optional argument from 0 to 6 to specify that
the return value includes a fractional seconds part of that
many digits.
Syntax for temporal literals produces temporal values:
DATE ',
str'TIME ',
and str'TIMESTAMP
', and the
ODBC-syntax equivalents. The resulting value includes a
trailing fractional seconds part if specified. Previously,
the temporal type keyword was ignored and these constructs
produced the string value. See
Standard SQL and ODBC Date and Time Literals
str'
In some cases, previously accepted syntax may produce different results. The following items indicate where existing code may need to be changed to avoid problems:
Some expressions produce results that differ from previous
results. Examples: The timestamp system
variable returns a value that includes a microseconds
fractional part rather than an integer. Functions that
return a result that includes the current time (such as
CURTIME(),
SYSDATE(), or
UTC_TIMESTAMP()) interpret an
argument as an fsp value and the
return value includes a fractional seconds part of that many
digits. Previously, these functions permitted an argument
but ignored it.
TIME values are converted to
DATETIME by adding the time
to the current date. (This means that the date part of the
result differs from the current date if the time value is
outside the range from '00:00:00' to
'23:59:59'.) Previously, conversion of
TIME values to
DATETIME was unreliable. See
Section 11.3.7, “Conversion Between Date and Time Types”.
TIMESTAMP(
was permitted in old MySQL versions, but
N)N was a display width rather than
fractional seconds precision. Support for this behavior was
removed in MySQL 5.5.3, so applications that are reasonably
up to date should not be subject to this issue. Otherwise,
code must be rewritten.