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From "Rick Hillegas (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-4107) DATE function returns wrong result for integer argument
Date Tue, 18 Aug 2009 13:22:14 GMT

     [ https://issues.apache.org/jira/browse/DERBY-4107?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Rick Hillegas updated DERBY-4107:

           Component/s:     (was: SQL)
    Bug behavior facts:   (was: [Wrong query result])

I am changing this from a SQL bug to a docs bug. The documentation says that the DATE() function,
applied to positive integer arguments, results in days counting up from the first day of the
common era. This is not true. The days count up from the beginning of the UNIX epoch, that
is, January 1, 1970. I think there is a typo in the documentation.

Note that the highest integer argument which you can pass to the DATE function is 2932897.
That many days after the start of the UNIX epoch is 9999-12-31, I think. At least my back
of the envelope calculation, which doesn't account for leap days, comes in around there. If
DATE were counting from the beginning of the common era, then DATE( 2932897 ) would be something
like 8029-12-31.

I am also unchecking the "wrong query result" box. I can't find this function in the SQL standard
and I don't see any industry consensus about how DATE should behave when applied to integer
arguments. I don't see any compelling reason to change Derby's behavior to something different,
particularly since that kind of change would create compatibility problems.

> DATE function returns wrong result for integer argument
> -------------------------------------------------------
>                 Key: DERBY-4107
>                 URL: https://issues.apache.org/jira/browse/DERBY-4107
>             Project: Derby
>          Issue Type: Bug
>          Components: Documentation
>    Affects Versions:
>         Environment: MS Windows XP Professional Version 2002 Service Pack 2, running
NetBeans IDE 6.5
>            Reporter: Nelson Rodrigues
>            Assignee: Yun Lee
> When Derby Reference Manual, version 10.4, lists Derby limitations for DATE is said that
the smallest DATE value is 0001-01-01 and the largest DATE value is 9999-12-31.
> When the same manual explains the DATE function is said that:
> "The argument must be ... a positive number less than or equal to 2,932,897 ... The result
is the date that is n-1 days after January 1, 0001, where n is the integral part of the number."
> Testing for the largest integer returns the expected result:
> select date(2932897) from SYSIBM.SYSDUMMY1   returns 9999-12-31 -> OK
> The problem comes when testing the smallest integer. We get a result different than we
> select date(1) from SYSIBM.SYSDUMMY1   returns 1970-01-01, but it should have returned
> The smallest date we get using integer as an argument to date function should be the
same we get when using the smallest string representation as an argument. In other words date(1)
should be equal to date('0001-01-01'). 
> select date('0001-01-01') from SYSIBM.SYSDUMMY1  returns 0001-01-01 -> OK

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