Question

We are using Oracle 11g and we have a table with a timestamp column which doesn’t contain the timezone (simply defined as TIMESTAMP). The timezone is written in a different column.

I want to be able to use the ‘max’ function while taking the timezone into account.
There’s probably a function to convert timezones easily and I just don’t know it.

I want to be able to do something like this:

SELECT max(covert_to_timezone(my_timestamp, my_timezone, 'GMT')) FROM my_table

How can I do that?

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Solution: According to Ajith Sasidharan’s answer:

SELECT max(from_tz(my_timestamp, my_timezone) at time zone '0:00') FROM my_table

Update: If you want to compare dates, simply use ‘cast’:

SELECT max(from_tz(cast(my_date as timestamp), my_timezone) at time zone '0:00') FROM my_table

Btw, now I got ‘ORA 01878’ errors, meaning our table contains invalid times (DST shit).

Answer 1

I guess you want a function like this ::

select to_char((from_tz(to_timestamp(to_char(DATABASE_DATE, 'YYYY-MM-DD HH:MI:SS PM'), 'YYYY-MM-DD HH:MI:SS PM') ,'America/New_York')
    at time zone 'America/Los_Angeles'),'YYYY-MM-DD HH:MI:SS PM TZD') as localtime
    from table