11.1.3 日期和时间字面量
Date and time values can be represented in several formats, such as quoted strings or as numbers, depending on the exact type of the value and other factors. For example, in contexts where MySQL expects a date, it interprets any of '2015-07-21'
, '20150721'
, and 20150721
as a date.
This section describes the acceptable formats for date and time literals. For more information about the temporal data types, such as the range of permitted values, see Section 13.2, “Date and Time Data Types”.
Standard SQL and ODBC 日期和时间字面量
Standard SQL requires temporal literals to be specified using a type keyword and a string. The space between the keyword and string is optional.
DATE 'str'
TIME 'str'
TIMESTAMP 'str'
MySQL recognizes but, unlike standard SQL, does not require the type keyword. Applications that are to be standard-compliant should include the type keyword for temporal literals.
MySQL also recognizes the ODBC syntax corresponding to the standard SQL syntax:
{ d 'str' }
{ t 'str' }
{ ts 'str' }
MySQL uses the type keywords and the ODBC constructions to produce DATE
, TIME
, and DATETIME
values, respectively, including a trailing fractional seconds part if specified. The TIMESTAMP
syntax produces a DATETIME
value in MySQL because DATETIME
has a range that more closely corresponds to the standard SQL TIMESTAMP
type, which has a year range from 0001
to 9999
. (The MySQL TIMESTAMP
year range is 1970
to 2038
.)
String and 数字字面量 in Date and Time Context
MySQL recognizes DATE
values in these formats:
-
As a string in either
'
orYYYY-MM-DD
''
format. A “relaxed” syntax is permitted, but is deprecated: Any punctuation character may be used as the delimiter between date parts. For example,YY-MM-DD
''2012-12-31'
,'2012/12/31'
,'2012^12^31'
, and'2012@12@31'
are equivalent. Using any character other than the dash (-
) as the delimiter raises a warning, as shown here:mysql> SELECT DATE'2012@12@31'; +------------------+ | DATE'2012@12@31' | +------------------+ | 2012-12-31 | +------------------+ 1 row in set, 1 warning (0.00 sec) mysql> SHOW WARNINGS\G *************************** 1. row *************************** Level: Warning Code: 4095 Message: Delimiter '@' in position 4 in datetime value '2012@12@31' at row 1 is deprecated. Prefer the standard '-'. 1 row in set (0.00 sec)
-
As a string with no delimiters in either
'
orYYYYMMDD
''
format, provided that the string makes sense as a date. For example,YYMMDD
''20070523'
and'070523'
are interpreted as'2007-05-23'
, but'071332'
is illegal (it has nonsensical month and day parts) and becomes'0000-00-00'
. -
As a number in either
YYYYMMDD
orYYMMDD
format, provided that the number makes sense as a date. For example,19830905
and830905
are interpreted as'1983-09-05'
.
MySQL recognizes DATETIME
and TIMESTAMP
values in these formats:
-
As a string in either
'
orYYYY-MM-DD hh:mm:ss
''
format. MySQL also permits a “relaxed” syntax here, although this is deprecated: Any punctuation character may be used as the delimiter between date parts or time parts. For example,YY-MM-DD hh:mm:ss
''2012-12-31 11:30:45'
,'2012^12^31 11+30+45'
,'2012/12/31 11*30*45'
, and'2012@12@31 11^30^45'
are equivalent. Use of any characters as delimiters in such values, other than the dash (-
) for the date part and the colon (:
) for the time part, raises a warning, as shown here:mysql> SELECT TIMESTAMP'2012^12^31 11*30*45'; +--------------------------------+ | TIMESTAMP'2012^12^31 11*30*45' | +--------------------------------+ | 2012-12-31 11:30:45 | +--------------------------------+ 1 row in set, 1 warning (0.00 sec) mysql> SHOW WARNINGS\G *************************** 1. row *************************** Level: Warning Code: 4095 Message: Delimiter '^' in position 4 in datetime value '2012^12^31 11*30*45' at row 1 is deprecated. Prefer the standard '-'. 1 row in set (0.00 sec)
The only delimiter recognized between a date and time part and a fractional seconds part is the decimal point.
The date and time parts can be separated by
T
rather than a space. For example,'2012-12-31 11:30:45'
'2012-12-31T11:30:45'
are equivalent.Previously, MySQL supported arbitrary numbers of leading and trailing whitespace characters in date and time values, as well as between the date and time parts of
DATETIME
andTIMESTAMP
values. In MySQL 8.4, this behavior is deprecated, and the presence of excess whitespace characters triggers a warning, as shown here:mysql> SELECT TIMESTAMP'2012-12-31 11-30-45'; +----------------------------------+ | TIMESTAMP'2012-12-31 11-30-45' | +----------------------------------+ | 2012-12-31 11:30:45 | +----------------------------------+ 1 row in set, 1 warning (0.00 sec) mysql> SHOW WARNINGS\G *************************** 1. row *************************** Level: Warning Code: 4096 Message: Delimiter ' ' in position 11 in datetime value '2012-12-31 11-30-45' at row 1 is superfluous and is deprecated. Please remove. 1 row in set (0.00 sec)
A warning is also raised when whitespace characters other than the space character is used, like this:
mysql> SELECT TIMESTAMP'2021-06-06 '> 11:15:25'; +--------------------------------+ | TIMESTAMP'2021-06-06 11:15:25' | +--------------------------------+ | 2021-06-06 11:15:25 | +--------------------------------+ 1 row in set, 1 warning (0.00 sec) mysql> SHOW WARNINGS\G *************************** 1. row *************************** Level: Warning Code: 4095 Message: Delimiter '\n' in position 10 in datetime value '2021-06-06 11:15:25' at row 1 is deprecated. Prefer the standard ' '. 1 row in set (0.00 sec)
Only one such warning is raised per temporal value, even though multiple issues may exist with delimiters, whitespace, or both, as shown in the following series of statements:
mysql> SELECT TIMESTAMP'2012!-12-31 11:30:45'; +----------------------------------+ | TIMESTAMP'2012!-12-31 11:30:45' | +----------------------------------+ | 2012-12-31 11:30:45 | +----------------------------------+ 1 row in set, 1 warning (0.00 sec) mysql> SHOW WARNINGS\G *************************** 1. row *************************** Level: Warning Code: 4095 Message: Delimiter '!' in position 4 in datetime value '2012!-12-31 11:30:45' at row 1 is deprecated. Prefer the standard '-'. 1 row in set (0.00 sec) mysql> SELECT TIMESTAMP'2012-12-31 11:30:45'; +---------------------------------+ | TIMESTAMP'2012-12-31 11:30:45' | +---------------------------------+ | 2012-12-31 11:30:45 | +---------------------------------+ 1 row in set, 1 warning (0.00 sec) mysql> SHOW WARNINGS\G *************************** 1. row *************************** Level: Warning Code: 4096 Message: Delimiter ' ' in position 11 in datetime value '2012-12-31 11:30:45' at row 1 is superfluous and is deprecated. Please remove. 1 row in set (0.00 sec) mysql> SELECT TIMESTAMP'2012-12-31 11:30:45'; +--------------------------------+ | TIMESTAMP'2012-12-31 11:30:45' | +--------------------------------+ | 2012-12-31 11:30:45 | +--------------------------------+ 1 row in set (0.00 sec)
-
As a string with no delimiters in either
'
orYYYYMMDDhhmmss
''
format, provided that the string makes sense as a date. For example,YYMMDDhhmmss
''20070523091528'
and'070523091528'
are interpreted as'2007-05-23 09:15:28'
, but'071122129015'
is illegal (it has a nonsensical minute part) and becomes'0000-00-00 00:00:00'
. -
As a number in either
YYYYMMDDhhmmss
orYYMMDDhhmmss
format, provided that the number makes sense as a date. For example,19830905132800
and830905132800
are interpreted as'1983-09-05 13:28:00'
.
A DATETIME
or TIMESTAMP
value can include a trailing fractional seconds part in up to microseconds (6 digits) precision. The fractional part should always be separated from the rest of the time by a decimal point; no other fractional seconds delimiter is recognized. For information about fractional seconds support in MySQL, see Section 13.2.6, “Fractional Seconds in Time Values”.
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
70-99
become1970-1999
. -
Year values in the range
00-69
become2000-2069
.
See also Section 13.2.9, “2-Digit Years in Dates”.
For values specified as strings that include date part delimiters, it is unnecessary to specify two digits for month or day values that are less than 10
. '2015-6-9'
is the same as '2015-06-09'
. Similarly, for values specified as strings that include time part delimiters, it is unnecessary to specify two digits for hour, minute, or second values that are less than 10
. '2015-10-30 1:2:3'
is the same as '2015-10-30 01:02:03'
.
Values specified as numbers should be 6, 8, 12, or 14 digits long. If a number is 8 or 14 digits long, it is assumed to be in YYYYMMDD
or YYYYMMDDhhmmss
format and that the year is given by the first 4 digits. If the number is 6 or 12 digits long, it is assumed to be in YYMMDD
or YYMMDDhhmmss
format and that the year is given by the first 2 digits. Numbers that are not one of these lengths are interpreted as though padded with leading zeros to the closest length.
Values specified as nondelimited strings are interpreted according their length. For a string 8 or 14 characters long, the year is assumed to be given by the first 4 characters. Otherwise, the year is assumed to be given by the first 2 characters. The string is interpreted from left to right to find year, month, day, hour, minute, and second values, for as many parts as are present in the string. This means you should not use strings that have fewer than 6 characters. For example, if you specify '9903'
, thinking that represents March, 1999, MySQL converts it to the “zero” date value. This occurs because the year and month values are 99
and 03
, but the day part is completely missing. However, you can explicitly specify a value of zero to represent missing month or day parts. For example, to insert the value '1999-03-00'
, use '990300'
.
MySQL recognizes TIME
values in these formats:
-
As a string in
'D hh:mm:ss'
format. You can also use one of the following “relaxed” syntaxes:'hh:mm:ss'
,'hh:mm'
,'D hh:mm'
,'D hh'
, or'ss'
. HereD
represents days and can have a value from 0 to 34. -
As a string with no delimiters in
'hhmmss'
format, provided that it makes sense as a time. For example,'101112'
is understood as'10:11:12'
, but'109712'
is illegal (it has a nonsensical minute part) and becomes'00:00:00'
. -
As a number in
hhmmss
format, provided that it makes sense as a time. For example,101112
is understood as'10:11:12'
. The following alternative formats are also understood:ss
,mmss
, orhhmmss
.
A trailing fractional seconds part is recognized in the 'D hh:mm:ss.fraction'
, 'hh:mm:ss.fraction'
, 'hhmmss.fraction'
, and hhmmss.fraction
time formats, where fraction
is the fractional part in up to microseconds (6 digits) precision. The fractional part should always be separated from the rest of the time by a decimal point; no other fractional seconds delimiter is recognized. For information about fractional seconds support in MySQL, see Section 13.2.6, “Fractional Seconds in Time Values”.
For TIME
values specified as strings that include a time part delimiter, it is unnecessary to specify two digits for hours, minutes, or seconds values that are less than 10
. '8:3:2'
is the same as '08:03:02'
.
You can specify a time zone offset when inserting TIMESTAMP
and DATETIME
values into a table. The offset is appended to the time part of a datetime literal, with no intravening spaces, and uses the same format used for setting the time_zone
system variable, with the following exceptions:
-
For hour values less than 10, a leading zero is required.
-
The value
'-00:00'
is rejected. -
Time zone names such as
'EET'
and'Asia/Shanghai'
cannot be used;'SYSTEM'
also cannot be used in this context.
The value inserted must not have a zero for the month part, the day part, or both parts. This is enforced regardless of the server SQL mode setting.
This example illustrates inserting datetime values with time zone offsets into TIMESTAMP
and DATETIME
columns using different time_zone
settings, and then retrieving them:
mysql> CREATE TABLE ts (
-> id INTEGER NOT NULL AUTO_INCREMENT PRIMARY KEY,
-> col TIMESTAMP NOT NULL
-> ) AUTO_INCREMENT = 1;
mysql> CREATE TABLE dt (
-> id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
-> col DATETIME NOT NULL
-> ) AUTO_INCREMENT = 1;
mysql> SET @@time_zone = 'SYSTEM';
mysql> INSERT INTO ts (col) VALUES ('2020-01-01 10:10:10'),
-> ('2020-01-01 10:10:10+05:30'), ('2020-01-01 10:10:10-08:00');
mysql> SET @@time_zone = '+00:00';
mysql> INSERT INTO ts (col) VALUES ('2020-01-01 10:10:10'),
-> ('2020-01-01 10:10:10+05:30'), ('2020-01-01 10:10:10-08:00');
mysql> SET @@time_zone = 'SYSTEM';
mysql> INSERT INTO dt (col) VALUES ('2020-01-01 10:10:10'),
-> ('2020-01-01 10:10:10+05:30'), ('2020-01-01 10:10:10-08:00');
mysql> SET @@time_zone = '+00:00';
mysql> INSERT INTO dt (col) VALUES ('2020-01-01 10:10:10'),
-> ('2020-01-01 10:10:10+05:30'), ('2020-01-01 10:10:10-08:00');
mysql> SET @@time_zone = 'SYSTEM';
mysql> SELECT @@system_time_zone;
+--------------------+
| @@system_time_zone |
+--------------------+
| EST |
+--------------------+
mysql> SELECT col, UNIX_TIMESTAMP(col) FROM dt ORDER BY id;
+---------------------+---------------------+
| col | UNIX_TIMESTAMP(col) |
+---------------------+---------------------+
| 2020-01-01 10:10:10 | 1577891410 |
| 2019-12-31 23:40:10 | 1577853610 |
| 2020-01-01 13:10:10 | 1577902210 |
| 2020-01-01 10:10:10 | 1577891410 |
| 2020-01-01 04:40:10 | 1577871610 |
| 2020-01-01 18:10:10 | 1577920210 |
+---------------------+---------------------+
mysql> SELECT col, UNIX_TIMESTAMP(col) FROM ts ORDER BY id;
+---------------------+---------------------+
| col | UNIX_TIMESTAMP(col) |
+---------------------+---------------------+
| 2020-01-01 10:10:10 | 1577891410 |
| 2019-12-31 23:40:10 | 1577853610 |
| 2020-01-01 13:10:10 | 1577902210 |
| 2020-01-01 05:10:10 | 1577873410 |
| 2019-12-31 23:40:10 | 1577853610 |
| 2020-01-01 13:10:10 | 1577902210 |
+---------------------+---------------------+
The offset is not displayed when selecting a datetime value, even if one was used when inserting it.
The range of supported offset values is -13:59
to +14:00
, inclusive.
Datetime literals that include time zone offsets are accepted as parameter values by prepared statements.