主页 / dba / 问题 / 138080
Accepted
Michael Green
Asked: 2016-05-10 21:29:51 +0800 CST

将日期范围转换为间隔描述

  • 772

最近的一个项目中的一项要求是报告资源何时会被完全消耗。除了用尽日历日期外，我还被要求以类似英语的格式显示剩余时间，例如“1 year, 3 months to go”。

内置DATEDIFF函数

返回指定开始日期和结束日期之间跨越的指定日期部分边界的计数。

如果按原样使用，可能会产生误导或混淆的结果。例如，使用 YEAR 的间隔将显示 1999-12-31 (YYYY-MM-DD) 和 2000-01-01 相隔一年，而常识会说这些日期仅相隔 1 天。相反，使用 DAY 1999-12-31 和 2010-12-31 的间隔相隔 4,018 天，而大多数人会将“11 年”视为更好的描述。

从天数开始计算月份和年份，容易出现闰年和月份大小错误。

我想知道如何在各种 SQL 方言中实现这一点？示例输出包括：

create table TestData(
    FromDate date not null,
    ToDate date not null,
    ExpectedResult varchar(100) not null); -- exact formatting is unimportant

insert TestData (FromDate, ToDate, ExpectedResult)
values ('1999-12-31', '1999-12-31', '0 days'),
       ('1999-12-31', '2000-01-01', '1 day'),
       ('2000-01-01', '2000-02-01', '1 month'),
       ('2000-02-01', '2000-03-01', '1 month'),              -- month length not important
       ('2000-01-28', '2000-02-29', '1 month, 1 day'),       -- leap years to be accounted for
       ('2000-01-01', '2000-12-31', '11 months, 30 days'),
       ('2000-02-28', '2000-03-01', '2 days'),
       ('2001-02-28', '2001-03-01', '1 day'),                -- not a leap year
       ('2000-01-01', '2001-01-01', '1 year'),
       ('2000-01-01', '2011-01-01', '11 years'),
       ('9999-12-30', '9999-12-31', '1 day'),                -- catch overflow in date calculations
       ('1900-01-01', '9999-12-31', '8099 years 11 months 30 days');  -- min(date) to max(date)

我碰巧使用的是 SQL Server 2008R2，但我有兴趣了解其他方言如何处理这个问题。

database-agnostic date-format

5 个回答

  1. 此答案显示了使用 SQL Server (2005+) CLR 函数的实现。

    -- Enable CLR (if necessary)
EXECUTE sys.sp_configure 
    @configname = 'clr enabled',
    @configvalue = 1;

RECONFIGURE;

    组装和功能

    CREATE ASSEMBLY DBA
AUTHORIZATION dbo
FROM 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WITH PERMISSION_SET = SAFE;
GO
CREATE FUNCTION dbo.IntervalDescription
(
    @From date, 
    @To date
)
RETURNS nvarchar(100)
AS EXTERNAL NAME 
    DBA.UserDefinedFunctions.IntervalDescription;

    用法

    SELECT 
    TD.FromDate,
    TD.ToDate,
    TD.ExpectedResult, 
    IntervalDescription = dbo.IntervalDescription(TD.FromDate, TD.ToDate) 
FROM dbo.TestData AS TD;

    结果

    计划

    输出

    资源

    我不是 C# 程序员！

    using Microsoft.SqlServer.Server;
using System;
using System.Text;

public partial class UserDefinedFunctions
{
    [SqlFunction
        (
        DataAccess = DataAccessKind.None,
        SystemDataAccess = SystemDataAccessKind.None,
        IsDeterministic = true,
        IsPrecise = true,
        Name = "IntervalDescription"
        )
    ]
    [return: SqlFacet(IsFixedLength = false, IsNullable = false, MaxSize = 100)]
    public static string IntervalDescription(DateTime From, DateTime To)
    {
        var workDate = From;
        int years = To.Year - From.Year;
        int months = 0;
        int days = 0;

        if (years != 0)
        {
            if (From.Month > To.Month || (From.Month == To.Month && From.Day > To.Day))
            {
                years--;
            }
            workDate = workDate.AddYears(years);
        }

        while (workDate < To && (workDate.Year != DateTime.MaxValue.Year || workDate.Month != DateTime.MaxValue.Month))
        {
            if (workDate.AddMonths(1) <= To)
            {
                months++;
                workDate = workDate.AddMonths(1);
            }
            else
            {
                break;
            }
        }

        while (workDate < To)
        {
            days++;
            workDate = workDate.AddDays(1);
        }

        StringBuilder sb = new StringBuilder(100);

        if (years > 0)
        {
            sb.Append(years);
            sb.Append(years == 1 ? " year" : " years");
            sb.Append((months > 0 || days > 0) ? ", " : string.Empty);
        }

        if (months > 0)
        {
            sb.Append(months);
            sb.Append(months == 1 ? " month" : " months");
            sb.Append(days > 0 ? ", " : string.Empty);
        }

        if (days > 0 || (years == 0 && months == 0))
        {
            sb.Append(days);
            sb.Append(days == 1 ? " day" : " days");
        }

        return
            sb.ToString();

    }
}
    • 11
  2. Best Answer

    以下解决方案适用于 SQL Server。该方法与Serg 的方法相似，因为查询仅使用 DATEADD 和 DATEDIFF 函数。但是，它不考虑负间隔（FromDate > ToDate），它从总月差中得出年份和月份：

    WITH
  MonthDiff AS
  (
    SELECT
      t.FromDate,
      t.ToDate,
      t.ExpectedResult,
      Months = x.Months - CASE WHEN DAY(t.FromDate) > DAY(t.ToDate) THEN 1 ELSE 0 END
    FROM
      dbo.TestData AS t
      CROSS APPLY (SELECT DATEDIFF(MONTH, t.FromDate, t.ToDate)) AS x (Months)
  )
SELECT
  t.FromDate,
  t.ToDate,
  t.ExpectedResult,
  Result = ISNULL(NULLIF(ISNULL(x.Years  + CASE x.Years  WHEN '1' THEN ' year '  ELSE ' years '  END, '')
                       + ISNULL(x.Months + CASE x.Months WHEN '1' THEN ' month ' ELSE ' months ' END, '')
                       + ISNULL(x.Days   + CASE x.Days   WHEN '1' THEN ' day '   ELSE ' days '   END, ''), ''), '0 days')
FROM
  MonthDiff AS t
  CROSS APPLY
  (
    SELECT
      CAST(NULLIF(t.Months / 12, 0) AS varchar(10)),
      CAST(NULLIF(t.Months % 12, 0) AS varchar(10)),
      CAST(NULLIF(DATEDIFF(DAY, DATEADD(MONTH, t.Months, t.FromDate), t.ToDate), 0) AS varchar(10))
  ) AS x (Years, Months, Days)
;

    输出：

    FromDate    ToDate      ExpectedResult                 Result
----------  ----------  -----------------------------  -----------------------------
1999-12-31  1999-12-31  0 days                         0 days
1999-12-31  2000-01-01  1 day                          1 day 
2000-01-01  2000-02-01  1 month                        1 month 
2000-02-01  2000-03-01  1 month                        1 month 
2000-01-28  2000-02-29  1 month, 1 day                 1 month 1 day 
2000-01-01  2000-12-31  11 months, 30 days             11 months 30 days 
2000-02-28  2000-03-01  2 days                         2 days 
2001-02-28  2001-03-01  1 day                          1 day 
2000-01-01  2001-01-01  1 year                         1 year 
2000-01-01  2011-01-01  11 years                       11 years 
9999-12-30  9999-12-31  1 day                          1 day 
1900-01-01  9999-12-31  8099 years 11 months 30 days   8099 years 11 months 30 days
    • 11

  3. 我的版本，在 SQL Server 2008R2 SP2 中实现。

    CREATE FUNCTION dbo.ReadableInterval(
    @FromDate AS date,
    @ToDate AS date
)
RETURNS TABLE AS RETURN 
(
with YearStep as
(
    select
        max(n1.Number) as YearNumber
    from dbo.Numbers as n1
    where n1.Number <= DATEDIFF(YEAR, @FromDate, @ToDate)  -- see comment (A)
    and DATEADD(YEAR, n1.Number, @FromDate) <= @ToDate     -- see comment (B)
)
, MonthStep as
(
    select
        max(n2.Number) as MonthNumber
    from dbo.Numbers as n2
    cross apply YearStep as y1
    where n2.Number <= DATEDIFF(MONTH, DATEADD(YEAR, y1.YearNumber, @FromDate), @ToDate)
    and DATEADD(MONTH, n2.Number, DATEADD(YEAR, y1.YearNumber, @FromDate)) <= @ToDate
)
, DayStep as
(
    select
        DATEDIFF(day, DATEADD(MONTH, m1.MonthNumber, DATEADD(YEAR, y2.YearNumber, @FromDate)), @ToDate) as DayNumber
    from MonthStep as m1
    cross apply YearStep as y2
)
select
    y.YearNumber,
    m.MonthNumber,
    d.DayNumber
from YearStep as y
cross apply MonthStep as m
cross apply DayStep as d
)

    使用给定的测试数据，结果是

    select
    td.FromDate,
    td.ToDate,
    td.ExpectedResult,
    ri.YearNumber as Years,
    ri.MonthNumber as Months,
    ri.DayNumber as [Days]
from dbo.TestData as td
cross apply dbo.ReadableInterval(td.FromDate, td.ToDate) as ri;

    FromDate   ToDate     ExpectedResult               Years Months Days
---------- ---------- ---------------------------- ----- ------ ----
1999-12-31 1999-12-31 0 days                           0      0    0
1999-12-31 2000-01-01 1 day                            0      0    1
2000-01-01 2000-02-01 1 month                          0      1    0
2000-02-01 2000-03-01 1 month                          0      1    0
2000-01-28 2000-02-29 1 month, 1 day                   0      1    1
2000-01-01 2000-12-31 11 months, 30 days               0     11   30
2000-02-28 2000-03-01 2 days                           0      0    2
2001-02-28 2001-03-01 1 day                            0      0    1
2000-01-01 2001-01-01 1 year                           1      0    0
2000-01-01 2011-01-01 11 years                        11      0    0
9999-12-30 9999-12-31 1 day                            0      0    1
1900-01-01 9999-12-31 8099 years 11 months 30 days  8099     11   30

    解释

    我的一般方法是从较早的日期开始，首先是几年，然后是几个月，然后是几天。在每个粒度级别，目标是尽可能接近结束日期而不超过它，然后在下一个较低级别继续。

    我使用数字表来促进接近但未结束的计算。从这张表中，我可以找到代码中注释（B）DATEADD之前的最大年/月/天数。ToDate

    由于我在寻找 MAX 数并且我的 Numbers 表聚集在它上面，因此优化器正在执行降序扫描，将值提供给 DATEADD。这会导致日期溢出错误，因为 Numbers 包含超过 100,000 行。DATEADD(YEAR, 100000, @FromDate)大于 9999-12-31 并引发错误。谓词 (A) 给出了向后扫描开始的 Number 值的上限，避免了日期溢出。因此，即使是非常大的日期范围，查询计划也会遍历非常少的行。

    这种方法用于查找年份和月份，除了我在第一个 CTE 中找到的年份，月份的起点提前了。DAYS 是我的最低粒度级别，所以一个简单的 DATEDIFF 就足够了。

    这可以扩展到更精细的粒度，如果需要，以小时、分钟和秒为单位返回间隔。

    • 9

  4. PostgreSQL 支持age开箱即用的功能：

    select
  FromDate,
  ToDate,
  ExpectedResult,
  age(ToDate, FromDate)
from TestData;

    这给出了期望的结果，给予或接受一些额外的时间值。

    FromDate      ToDate        ExpectedResult                  age
----------    ----------    ----------------------------    --------------------------
1999-12-31    1999-12-31    0 days                          00:00:00
1999-12-31    2000-01-01    1 day                           1 day
2000-01-01    2000-02-01    1 month                         1 mon
2000-02-01    2000-03-01    1 month                         1 mon
2000-01-28    2000-02-29    1 month, 1 day                  1 mon 1 day
2000-01-01    2000-12-31    11 months, 30 days              11 mons 30 days
2000-02-28    2000-03-01    2 days                          2 days
2001-02-28    2001-03-01    1 day                           1 day
2000-01-01    2001-01-01    1 year                          1 year
2000-01-01    2011-01-01    11 years                        11 years
9999-12-30    9999-12-31    1 day                           1 day
1900-01-01    9999-12-31    8099 years 11 months 30 days    8099 years 11 mons 30 days
    • 8

  5. 不需要number表格或计数的版本。对 Michael Green 的测试数据给出相同的结果。他们在数据上有所不同 @FromDate > @ToDate。 ReadableInterval2返回与空值相反的负值。

    CREATE FUNCTION dbo.ReadableInterval2(
    @FromDate AS date,
    @ToDate AS date
)
RETURNS TABLE AS RETURN 
(with checkData as (
    select 
       fromDate = case when @FromDate > @ToDate then @ToDate else @FromDate end,
       toDate = case when @FromDate <= @ToDate then @ToDate else @FromDate end,
       k = case when @FromDate > @ToDate then -1 else 1 end
), MonthStep as (
    select k, FromDate, ToDate,
        YearNumber = x.months / 12,
        MonthNumber = x.months % 12
    from checkdata
    cross apply(
        select months = DATEDIFF(MONTH, FromDate, ToDate)
            - case when DAY(FromDate) > DAY(ToDate) then 1 else 0 end
        ) x
)
select YearNumber = k*YearNumber, 
      MonthNumber = k*MonthNumber,
      DayNumber = k*DATEDIFF(day, DATEADD(MONTH, MonthNumber, DATEADD(YEAR, YearNumber, FromDate)), ToDate) 
    from MonthStep 
)
    • 6

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