[数据库基础]——快速浏览日期时间转换

数据库日期和时间类型

相互转换

time ⇌ date

time ⇌ smalldatetime

time ⇌ datetime

time ⇌ datetime2

time ⇌ datetimeoffset

date ⇌ smalldatetime

date ⇌ datetime

date ⇌ datetime2

date ⇌ datetimeoffset

smalldatetime ⇌ datetime

smalldatetime ⇌ datetime2

smalldatetime ⇌ datetimeoffset

datetime ⇌ datetime2

datetime ⇌ datetimeoffset

datetime2 ⇌ datetimeoffset

数据库日期和时间类型：

类型	格式	范围
time	hh:mm:ss[.nnnnnnn]	00:00:00.0000000 ~ 23:59:59.9999999
date	YYYY-MM-DD	0001-01-01 ~ 9999-12-31
smalldatetime	YYYY-MM-DD hh:mm:ss	1900-01-01 ~ 079-06-06
datetime	YYYY-MM-DD hh:mm:ss[.nnn]	1753-01-01 ~ 99-12-31
datetime2	YYYY-MM-DD hh:mm:ss[.nnnnnnn]	0001-01-01 00:00:00.0000000 ~ 99-12-31 23:59:59.9999999
datetimeoffset	YYYY-MM-DD hh:mm:ss[.nnnnnnn] [+\|-]hh:mm	0001-01-01 00:00:00.0000000 ~9999-12-31 23:59:59.9999999 (in UTC)

相互转换（SET DATEFORMAT dmy;）

time ⇌ date

   1:  -- time -> date

   2:  DECLARE @time time(4) = '12:15:04.1234';

   3:  DECLARE @date date= @time;

4:

   5:  SELECT @time AS '@time', @date AS '@date';

Result：

Operand type clash: time is incompatible with date

   1:  -- date -> time

   2:  DECLARE @date date= '12-10-25';

   3:  DECLARE @time time= @date;

4:

   5:  SELECT @date AS '@date', @time AS '@time';

Result：

Operand type clash: time is incompatible with date

time ⇌ smalldatetime

   1:  -- time -> smalldatetime

   2:  DECLARE @time time(4) = '12:15:04.1234';

   3:  DECLARE @smalldatetime smalldatetime= @time;

4:

   5:  SELECT @time AS '@time', @smalldatetime AS '@smalldatetime';

Result：

@time @smalldatetime
12:15:04.1234 1900-01-01 12:15:00

   1:  -- samlldatetime –> time

   2:  DECLARE @smalldatetime smalldatetime = '13-12-1995 12:43:10';

   3:  DECLARE @time time(4) = @smalldatetime;

4:

   5:  SELECT @smalldatetime AS '@smalldatetime', @time AS 'time';

Result：

@smalldatetime @time
1995-12-13 12:43:00 12:43:00.0000

time ⇌ datetime

   1:  -- time -> datetime

   2:  DECLARE @time time(4) = '12:10:05.1234';

   3:  DECLARE @datetime datetime = @time;

4:

   5:  SELECT @time AS '@datetime', @datetime AS '@time';

Result：

@time @datetime
12:10:05.1234 1900-01-01 12:10:05.123

   1:  -- datetime -> time

   2:  DECLARE @datetime datetime = '12-11-05 12:10:05.123';

   3:  DECLARE @time time(4) = @datetime;

4:

   5:  SELECT @datetime AS '@datetime', @time AS '@time';

Result：

@datetime @time
2005-11-12 12:10:05.123 12:10:05.1230

time ⇌ datetime2

   1:  -- time -> datetime2

   2:  DECLARE @time time(4) = '12:15:04.1234';

   3:  DECLARE @datetime2 datetime2(3) = @time;

4:

   5:  SELECT @datetime2 AS '@datetime2', @time AS '@time';

Result：

@time @datetime2
12:15:04.1234 1900-01-01 12:15:04.123

   1:  -- datetime2 -> time

   2:  DECLARE @datetime2 datetime2(4) = '12-10-25 12:32:10.1234';

   3:  DECLARE @time time(3) = @datetime2;

4:

   5:  SELECT @datetime2 AS '@datetime2', @time AS '@time(3)';

Result：

@datetime2 @time(3)
2025-10-12 12:32:10.1234 12:32:10.123

time ⇌ datetimeoffset

   1:  -- time -> datetimeoffset

   2:  DECLARE @time time(4) = '12:15:04.1234';

   3:  DECLARE @datetimeoffset datetimeoffset(3) = @time;

4:

   5:  SELECT @time AS '@time', @datetimeoffset AS '@datetimeoffset';

Result：

@time @datetimeoffset
12:15:04.1234 1900-01-01 12:15:04.123 +00:00

   1:  -- datetimeoffset -> time

   2:  DECLARE @datetimeoffset datetimeoffset(4) = '12-10-25 12:32:10.1234 +01:0';

   3:  DECLARE @time time(3) = @datetimeoffset;

4:

   5:  SELECT @datetimeoffset AS '@datetimeoffset ', @time AS '@time';

Result：

@datetimeoffset @time
2025-10-12 12:32:10.1234 +01:00 12:32:10.123

date ⇌ smalldatetime

   1:  -- date -> smalldatetime

   2:  DECLARE @date date= '1912-10-25';

   3:  DECLARE @smalldatetime smalldatetime = @date;

4:

   5:  SELECT @date AS '@date', @smalldatetime AS '@smalldatetime';

Result：

@date @smalldatetime
1912-10-25 1912-10-25 00:00:00

   1:  -- smalldatetime -> date

   2:  DECLARE @smalldatetime smalldatetime = '13-12-1955 12:43:10';

   3:  DECLARE @date date = @smalldatetime

4:

   5:  SELECT @smalldatetime AS '@smalldatetime', @date AS '@date';

Result：

@smalldatetime @date
1955-12-13 12:43:00 1955-12-13

date ⇌ datetime

   1:  -- date -> datetime

   2:  DECLARE @date date= '12-10-25';

   3:  DECLARE @datetime datetime= @date;

4:

   5:  SELECT @date AS '@date', @datetime AS '@datetime';

Result：

@date @datetime
2025-10-12 2025-10-12 00:00:00.000

   1:  -- datetime -> date

   2:  DECLARE @datetime datetime = '12-11-05 12:43:10';

   3:  DECLARE @date date = @datetime;

4:

   5:  SELECT @datetime AS '@datetime', @date AS '@date';

Result：

@datetime @date
2005-11-12 12:43:10.000 2005-11-12

date ⇌ datetime2

   1:  -- date -> datetime2

   2:  DECLARE @date date = '25-10-2030'

   3:  DECLARE @datetime2 datetime2(3) = @date;

4:

   5:  SELECT @date AS '@date', @datetime2 AS '@datetime2(3)';

Result：

@date @datetime2(3)
2030-10-25 2030-10-25 00:00:00.000

   1:  -- datetime2 -> date

   2:  DECLARE @datetime2 datetime2(4) = '12-10-25 12:32:10.1234';

   3:  DECLARE @date date = @datetime2;

4:

   5:  SELECT @datetime2 AS '@datetime2', @date AS '@date';

Result：

@datetime2 @date
2025-10-12 12:32:10.1234 2025-10-12

date ⇌ datetimeoffset

   1:  -- date -> datetimeoffset

   2:  DECLARE @date date = '1912-10-25';

   3:  DECLARE @datetimeoffset datetimeoffset(3) = @date;

4:

   5:  SELECT @date AS '@date', @datetimeoffset AS '@datetimeoffset';

Result：

@date @datetimeoffset
1912-10-25 1912-10-25 00:00:00.000 +00:00

   1:  -- datetimeoffset -> date

   2:  DECLARE @datetimeoffset datetimeoffset(4) = '12-10-25 12:32:10 +01:0';

   3:  DECLARE @date date= @datetimeoffset;

4:

   5:  SELECT @datetimeoffset AS '@datetimeoffset ', @date AS '@date';

Result：

@datetimeoffset @date
2025-10-12 12:32:10.0000 +01:00 2025-10-12

smalldatetime ⇌ datetime

   1:  -- smalldatetime -> datetime

   2:  DECLARE @smalldatetime smalldatetime = '12-10-2040 12:43:10';

   3:  DECLARE @datetime datetime = @smalldatetime;

4:

   5:  SELECT @smalldatetime AS '@smalldatetime', @datetime AS '@datetime';

Result：

@smalldatetime @datetime
2040-10-12 12:43:00 2040-10-12 12:43:00.000

   1:  -- datetime -> smalldatetime

   2:  DECLARE @datetime datetime = '12-11-05 12:43:10.123';

   3:  DECLARE @smalldatetime smalldatetime = @datetime;

4:

   5:  SELECT @datetime AS 'datetime', @smalldatetime AS '@smalldatetime';

Result：

datetime @smalldatetime
2005-11-12 12:43:10.123 2005-11-12 12:43:00

smalldatetime ⇌ datetime2

   1:  -- smalldatetime -> datetime2

   2:  DECLARE @smalldatetime smalldatetime = '12-06-2011 12:43:10';

   3:  DECLARE @datetime2 datetime2(4) = @smalldatetime;

4:

   5:  SELECT @smalldatetime AS '@smalldatetime', @datetime2 AS '@datetime2(4)';

Result：

@smalldatetime @datetime2(4)
2011-06-12 12:43:00 2011-06-12 12:43:00.0000

   1:  -- datetime2 -> smalldatetime

   2:  DECLARE @datetime2 datetime2 = '12-10-25 12:32:10.1234567';

   3:  DECLARE @smalldatetime smalldatetime = @datetime2;

4:

   5:  SELECT @datetime2 AS '@datetime2', @smalldatetime AS '@smalldatetime';

Result：

@datetime2 @smalldatetime
2025-10-12 12:32:10.1234567 2025-10-12 12:32:00

smalldatetime ⇌ datetimeoffset

   1:  -- samlldatetime -> datetimeoffset

   2:  DECLARE @smalldatetime smalldatetime = '12-10-2013 12:43:10';

   3:  DECLARE @datetimeoffset datetimeoffset(4) = @smalldatetime;

4:

   5:  SELECT @smalldatetime AS '@smalldatetime', @datetimeoffset AS '@datetimeoffset(4)';

Result：

@smalldatetime @datetimeoffset(4)
2013-10-12 12:43:00 2013-10-12 12:43:00.0000 +00:00

   1:  -- datetimeoffset -> smalldatetime

   2:  DECLARE @datetimeoffset datetimeoffset(3) = '1912-10-25 12:24:32 +10:0';

   3:  DECLARE @smalldatetime smalldatetime = @datetimeoffset;

4:

   5:  SELECT @datetimeoffset AS '@datetimeoffset', @smalldatetime AS '@smalldatetime';

Result：

@datetimeoffset @smalldatetime
1912-10-25 12:24:32.000 +10:00 1912-10-25 12:25:00

datetime ⇌ datetime2

   1:  -- datetimes -> datetime2

   2:  DECLARE @datetime datetime = '10-10-2014 12:45:37.123';

   3:  DECLARE @datetime2 datetime2(4) = @datetime;

4:

   5:  SELECT @datetime AS '@datetime', @datetime2 AS '@datetime2';

Result：

@datetime @datetime2
2014-10-10 12:45:37.123 2014-10-10 12:45:37.1230

   1:  -- datetimes2 -> datetime

   2:  DECLARE @datetime2 datetime2(4) = '1968-10-23 12:45:37.1237';

   3:  DECLARE @datetime datetime = @datetime2;

4:

   5:  SELECT @datetime2 AS '@datetime2', @datetime AS '@datetime';

Result：

@datetime2 @datetime
1968-10-23 12:45:37.1237 1968-10-23 12:45:37.123

datetime ⇌ datetimeoffset

   1:  -- datetime -> datetimeoffset

   2:  DECLARE @datetime datetime = '12-10-25 12:32:10.123';

   3:  DECLARE @datetimeoffset datetimeoffset = @datetime;

4:

   5:  SELECT @datetime AS '@datetime ', @datetimeoffset AS '@datetimeoffset';

Result：

@datetime @datetimeoffset
2025-10-12 12:32:10.123 2025-10-12 12:32:10.1230000 +00:00

   1:  -- datetimeoffset -> datetime

   2:  DECLARE @datetimeoffset datetimeoffset(4) = '12-10-25 12:32:10.1234 +01:0';

   3:  DECLARE @datetime datetime = @datetimeoffset;

4:

   5:  SELECT @datetimeoffset AS '@datetimeoffset ', @datetime AS '@datetime';

Result：

@datetimeoffset @datetime
2025-10-12 12:32:10.1234 +01:00 2025-10-12 12:32:10.123

datetime2 ⇌ datetimeoffset

   1:  -- datetime2 -> datetimeoffset

   2:  DECLARE @datetime2 datetime2(3) = '12-10-25 12:32:10.1234567';

   3:  DECLARE @datetimeoffset datetimeoffset(2) = @datetime2;

4:

   5:  SELECT @datetime2 AS '@datetime2', @datetimeoffset AS '@datetimeoffset(2)';

Result：

@datetime2 @datetimeoffset(2)
2025-10-12 12:32:10.123 2025-10-12 12:32:10.12 +00:00

   1:  -- datetimeoffset -> datetime2

   2:  DECLARE @datetimeoffset datetimeoffset(4) = '1912-10-25 12:24:32.1234 +10:0';

   3:  DECLARE @datetime2 datetime2(3)= @datetimeoffset;

4:

   5:  SELECT @datetimeoffset AS '@datetimeoffset', @datetime2 AS '@datetime2';

Result：

@datetimeoffset @datetime2
1912-10-25 12:24:32.1234 +10:00 1912-10-25 12:24:32.123

在此谢谢读完这篇博客，有什么写的不对的地方请指正。
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