Reading date only with PL/SQL from datetime field , from informix database

问题

I am having problem reading only the date with PL/SQL. The field that i want to read is datetime and its name is last_updated. I am doing comparation between oracle and informix databases and thats why i am using pl/sql. I have a query that looks and must work and its like this:

        select to_date("last_updated", 'dd/mm/YYYY')   from "smetka"@informix

This query is returning results, and it dont gives any error, but the format of the date is like this 30.06.0014 and must be 30.06.2014

回答1:

You will probably find that the database expected the date to be entered using the format dd/mm/yyyy but whatever application deposited used the format dd/mm/yy and trying to format it using dd/mm/yyyy the database just accepts it as being in the 1st century (rather than as expected the 21st century).

For example:

SELECT TO_DATE( '30/06/14', 'dd/mm/yy' )   AS date1,
       TO_DATE( '30/06/14', 'dd/mm/yyyy' ) AS date2
FROM   DUAL;

Outputs:

DATE1               DATE2
------------------- -------------------
2014-06-30 00:00:00 0014-06-30 00:00:00

You could try to correct it using something like this:

SELECT CASE
       WHEN TO_DATE( "last_updated", 'dd/mm/yyyy' )
              BETWEEN DATE '0000-01-01' AND DATE 0100-01-01'
       THEN TO_DATE( "last_updated", 'dd/mm/yyyy' ) + INTERVAL '2000' YEAR(4)
       ELSE TO_DATE( "last_updated", 'dd/mm/yyyy' )
       END
FROM   "smetka"@informix

SELECT CASE
       WHEN REGEXP_LIKE( "last_updated", '\d{1,2}/\d{1,2}/\d{1,2}' )
       THEN TO_DATE( "last_updated", 'dd/mm/yy' )
       ELSE TO_DATE( "last_updated", 'dd/mm/yyyy' )
       END
FROM   "smetka"@informix

来源：https://stackoverflow.com/questions/43583714/reading-date-only-with-pl-sql-from-datetime-field-from-informix-database

标签

Oracle

date

datetime

informix