How to subtract hours from a date in Oracle so it affects the day also

sql oracle date-arithmetic
hi4ppl picture hi4ppl · Jun 11, 2015 · Viewed 110.4k times · Source

I'm trying to subtract date from Oracle so it even effect the day as well. For example, if the timestamp is 01/June/2015 00 hours and if I subtract 2 hours, I want to be able to go to to 31/May/2014 22 hours.

I tried

to_char(sysdate-(2/11), 'MM-DD-YYYY HH24')

but it only subtracts the hour; it does not touch the day itself.

Answer

a_horse_with_no_name picture a_horse_with_no_name · Jun 11, 2015

Others have commented on the (incorrect) use of 2/11 to specify the desired interval.

I personally however prefer writing things like that using ANSI interval literals which makes reading the query much easier:

sysdate - interval '2' hour

It also has the advantage of being portable, many DBMS support this. Plus I don't have to fire up a calculator to find out how many hours the expression means - I'm pretty bad with mental arithmetics ;)

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