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https://issues.apache.org/jira/browse/DERBY-5065?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13015074#comment-13015074
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emmanuel chemla commented on DERBY-5065:
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Ok, at least, I believe that this behaviour should be documented, so that a
person using it like "datedif" to get amount of days, would be aware that he
could sometimes end up with "missing days" and hence, for such a use (i.e.
computation of simple days) a workaround is absolutely needed.
> timestampdiff doesn't differentiate between 28 march 2010 and 29 march 2010
> ---------------------------------------------------------------------------
>
> Key: DERBY-5065
> URL: https://issues.apache.org/jira/browse/DERBY-5065
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.7.1.1
> Environment: windows 7, the bug has been testified using ij tool and
> usign squirrel sql. My locales are "France"
> Reporter: emmanuel chemla
>
> I needed to accomplish a simple task with Derby : computing an interval of
> days (like datedif in excel).
> I used the TIMESTAMPDIFF function, it seemed to work well, until I noticed a
> strange behaviour : sometimes the computation is OK, sometimes not.
> After having searched the trouble, I've found that from TIMESTAMPDIFF's point
> of view, the 28 march 2010 is not a different day than the 29 march 2010.
> You can easily check it with this script in ij tool :
> -- creating testing environment
> CONNECT 'jdbc:derby:MyDbTestxyz;create=true';
> CREATE TABLE dummy (beginning DATE, ending DATE);
> INSERT INTO dummy (beginning, ending) VALUES ('2010-04-01', '2010-04-01');
> INSERT INTO dummy (beginning, ending) VALUES ('2010-03-31', '2010-04-01');
> INSERT INTO dummy (beginning, ending) VALUES ('2010-03-30', '2010-04-01');
> INSERT INTO dummy (beginning, ending) VALUES ('2010-03-29', '2010-04-01');
> INSERT INTO dummy (beginning, ending) VALUES ('2010-03-28', '2010-04-01');
> INSERT INTO dummy (beginning, ending) VALUES ('2010-03-27', '2010-04-01');
> INSERT INTO dummy (beginning, ending) VALUES ('2010-03-26', '2010-04-01');
> --
> -- checking the odd behaviour
> SELECT beginning, ending, {fn timestampdiff(SQL_TSI_DAY, beginning, ending )}
> AS "interval in days" FROM dummy;
> --
> -- cleaning
> DROP TABLE dummy
> You'll get this result :
> beginning ending interval in days
> 2010-04-01; 2010-04-01; 0
> 2010-03-31 ; 2010-04-01; 1
> 2010-03-30 ; 2010-04-01; 2
> 2010-03-29 ; 2010-04-01; 3
> 2010-03-28 ; 2010-04-01; 3 ??????
> 2010-03-27 ; 2010-04-01; 4 !
> 2010-03-26 ; 2010-04-01; 5 !
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