[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。
有帮助就推荐下，有感想就写下留言，不满意也写下留言，有问题及时更正。

时间： 2024-10-27 06:44:10

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