Hi, 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 of
2010.
You can easily check this with this script :
-- creating testing environment
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
Someone has any insight on this ? Is there a nicer way to get the interval
in days that won't get into this trouble ?
--
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