MySql 字符串时间转换

MySql中经常遇到字符串格式时间转换成时间类型的情况：

SELECT STR_TO_DATE('Jul 20 2013  7:49:14:610AM','%b %d %Y  %h:%i:%s:%f%p') from DUAL;

-- 执行后得到结果:
'2013-07-20 07:49:14.610000'

另外还有int值和时间变量相互转化的情况：

SELECT UNIX_TIMESTAMP(2009-4-5 12:50:58)  RROM DUAL;
-- 结果为:
1238907058

SELECT FROM_UNIXTIME(1238907058) FROM DUAL;
-- 结果为:
'2009-4-5 12:50:58'

还可以自定义输出格式：

SELECT FROM_UNIXTIME( 1234567890, '%Y-%m-%d %H:%i:%S' ) FROM DUAL;
--结果为:
'2009-02-14 07:31:30'

具体格式符号如下：

%W 星期名字(Sunday……Saturday)
%D 有英语前缀的月份的日期(1st, 2nd, 3rd, 等等。）
%Y 年, 数字, 4 位
%y 年, 数字, 2 位
%a 缩写的星期名字(Sun……Sat)
%d 月份中的天数, 数字(00……31)
%e 月份中的天数, 数字(0……31)
%m 月, 数字(01……12)
%c 月, 数字(1……12)
%b 缩写的月份名字(Jan……Dec)
%j 一年中的天数(001……366)
%H 小时(00……23)
%k 小时(0……23)
%h 小时(01……12)
%I 小时(01……12)
%l 小时(1……12)
%i 分钟, 数字(00……59)
%r 时间,12 小时(hh:mm:ss [AP]M)
%T 时间,24 小时(hh:mm:ss)
%S 秒(00……59)
%s 秒(00……59)
%f 毫秒(000...999)
%p AM或PM
%w 一个星期中的天数(0=Sunday ……6=Saturday ）
%U 星期(0……52), 这里星期天是星期的第一天
%u 星期(0……52), 这里星期一是星期的第一天
%% 一个文字“%”。

以下是官方文档的说明：

11.3.2. The

TIME

Type

MySQL retrieves and displays

TIME

values in

'HH:MM:SS'

format (or

'HHH:MM:SS'

format for large hours values).

TIME

values may range from

'-838:59:59'

to

'838:59:59'

. The hours part may be so large because the

TIME

type can be used not only to represent a time of day (which must be less than 24 hours), but also elapsed time or a time interval between two events (which may be much greater than 24 hours, or even negative).

You can specify

TIME

values in a variety of formats:

As a string in

'D HH:MM:SS.fraction'

format. You can also use one of the following “relaxed” syntaxes:

'HH:MM:SS.fraction'

,

'HH:MM:SS'

,

'HH:MM'

,

'D HH:MM:SS'

,

'D HH:MM'

,

'D HH'

, or

'SS'

. Here

D

represents days and can have a value from 0 to 34. Note that MySQL does not store the fraction part.

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

,

HHMMSS

,

HHMMSS.fraction

. Note that MySQL does not store the fraction part.

As the result of a function that returns a value that is acceptable in a

TIME

context, such as

CURRENT_TIME

.

For

TIME

values specified as strings that include a time part delimiter, it is not necessary 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'

.

Be careful about assigning abbreviated values to a

TIME

column. Without colons, MySQL interprets values using the assumption that the two rightmost digits represent seconds. (MySQL interprets

TIME

values as elapsed time rather than as time of day.) For example, you might think of

'1112'

and

1112

as meaning

'11:12:00'

(12 minutes after 11 o'clock), but MySQL interprets them as

'00:11:12'

(11 minutes, 12 seconds). Similarly,

'12'

and

12

are interpreted as

'00:00:12'

.

TIME

values with colons, by contrast, are always treated as time of the day. That is,

'11:12'

mean

'11:12:00'

, not

'00:11:12'

.

By default, values that lie outside the

TIME

range but are otherwise legal are clipped to the closest endpoint of the range. For
example,

'-850:00:00'

and

'850:00:00'

are converted to

'-838:59:59'

and

'838:59:59'

. Illegal

TIME

values are converted to

'00:00:00'

. Note that because

'00:00:00'

is itself a legal

TIME

value, there is no way to tell, from a value of

'00:00:00'

stored in a table, whether the original value was specified as

'00:00:00'

or whether it was illegal.