SQL Server：检查所选日期是否早于或晚于当前日期

Question

I am selecting data using the following stored procedure with dateDT being saved as datetime.

Is there a way I can use CASE to check for each of the selected dates whether it is older or newer than the current date and add a short text (eg 'past' or 'future') for this to the Select ?

SELECT      dateID,
            CONVERT(VARCHAR(11), dateDT, 106) AS dateDT,
            CONVERT(VARCHAR(10), dateDT, 126) AS dateDTShort,
            countries,
            regions
FROM        DaysFixed
WHERE       countries LIKE '%'+@selCountry+'%'
OR          regions LIKE '%'+@selCountry+'%'
ORDER BY    dateID
FOR XML PATH('datesDT'), ELEMENTS, TYPE, ROOT('root')

Many thanks in advance, Mike.

Answer 1

SELECT      dateID,
            CONVERT(VARCHAR(11), dateDT, 106) AS dateDT,
            CASE WHEN CONVERT(VARCHAR(11), dateDT, 106) > GETDATE() THEN 'Future' 
            ELSE 'Past' END AS FutureOrPast,
            CONVERT(VARCHAR(10), dateDT, 126) AS dateDTShort,
            countries,
            regions
FROM        DaysFixed
WHERE       countries LIKE '%'+@selCountry+'%'
OR          regions LIKE '%'+@selCountry+'%'
ORDER BY    dateID
FOR XML PATH('datesDT'), ELEMENTS, TYPE, ROOT('root')

Answer 2

Assuming that the field is a date:

SELECT      dateID,
            CONVERT(VARCHAR(11), dateDT, 106) AS dateDT,
            CONVERT(VARCHAR(10), dateDT, 126) AS dateDTShort,
            (CASE WHEN dateDT < GETDATE() then 'PAST' else 'FUTURE' end) as TimeWhen,
            countries,
            regions
FROM        DaysFixed
WHERE       countries LIKE '%'+@selCountry+'%'
OR          regions LIKE '%'+@selCountry+'%'
ORDER BY    dateID
FOR XML PATH('datesDT'), ELEMENTS, TYPE, ROOT('root')

If you just want to look at the date component, and not the time, and dateDT is a date and not a datetime :

            (CASE WHEN dateDT < cast(GETDATE() as date) THEN 'PAST'
                  WHEN dateDT = cast(GETDATE() as date) then 'PRESENT'
                  WHEN dateDT > cast(GETDATE() as date) THEN 'FUTURE'
             END) as TimeWhen

Note in these examples that no functions are applied to the dateDT column. This is a good habit to get into, although it does not make a difference for a case statement. When used in a where clause, however, it can make a big difference in performance.