Question

I’m using MS SQL Server 2005 and I need to store date values partially. For example, the day part of a date may remain unknown in fact but MS SQL Server constrains to specify the full date like the follow:

INSERT foo(dt) VALUES('2001-10-31');

I would like to use something like this though:

INSERT foo(dt) VALUES ('2001-10-??');

Of course, MS SQL cannot accept such a date, and I’ve found a rough example that converts date parts into multipliers:

SET NOCOUNT ON 
CREATE TABLE foo ( 
    dt INT 
) 
INSERT foo VALUES ( 
    DATEPART(YEAR, GETDATE()) * 10000 
        + DATEPART(MONTH, GETDATE()) * 100 
        + DATEPART(DAY, GETDATE()) 
) 
SELECT dt FROM foo 
DROP TABLE foo

… hm, I can’t believe whether it’s the only way to solve the problem, so I would like to ask: how do I resolve this issue in the best way?

Thanks in advance.

---

UPD 2014:
Also see Storing partial dates in a database

Answer 1

here you can store each date part, and still constrain them to a valid date:

CREATE Table PartialDates
(
     YearPart       smallint --(2 bytes -32k to +32k)
    ,MonthPart      tinyint  --(1 byte 0 to 255)
    ,DayPart        tinyint  --(1 byte 0 to 255)
    ,CompleteDate  AS (CONVERT(datetime,CONVERT(varchar(10),YearPart)+'-'+CONVERT(varchar(10),MonthPart)+'-'+CONVERT(varchar(10),coalesce(DayPart,1))))
)
ALTER TABLE dbo.PartialDates ADD CONSTRAINT
    CK_PartialDates_IsDate CHECK (ISDATE(CONVERT(varchar(10),YearPart)+'-'+CONVERT(varchar(10),MonthPart)+'-'+CONVERT(varchar(10),coalesce(DayPart,1)))=1)
GO

insert into PartialDates (yearpart,monthpart,daypart) values(2009,91,1) --error
insert into PartialDates (yearpart,monthpart,daypart) values(2009,1,1)  --ok
insert into PartialDates (yearpart,monthpart,daypart) values(2009,1,51) --error
insert into PartialDates (yearpart,monthpart,daypart) values(2009,2,29) --error
insert into PartialDates (yearpart,monthpart,daypart) values(2009,2,28) --ok
insert into PartialDates (yearpart,monthpart,daypart) values(2009,2,null)--ok

select * from PartialDates

YearPart MonthPart DayPart CompleteDate
-------- --------- ------- -----------------------
2009     1         1       2009-01-01 00:00:00.000
2009     2         28      2009-02-28 00:00:00.000
2009     2         NULL    2009-02-01 00:00:00.000

(3 row(s) affected