Using Oracle SQL, how does one output day number of week and day of week?

Question

Using Oracle SQL, how do you create a result set for:

Number for the Day Of The Week (1-7)
Name of the day (Monday, Tuesday, Wednesday, etc.)

For example:

DAY   NAME
1     Monday
2     Tuesday
3     Wednesday
4     Thursday
5     Friday
6     Saturday
7     Sunday

This was originally a very poorly worded question. However, it has been edited and clarified and is now a very useful question. The answers on this page were of great help to me with simplifying an (originally) difficult Oracle problem. These answers are not available elsewhere. This question deserves to be re-evaluated and possibly reopened. — JonathanDavidArndt

Alex Poole Alex Poole · Accepted Answer · 2013-01-25T09:02:36

Florin's answer is how I'd do it, but you need to be a little careful about NLS settings. The day of the week is affected by the NLS territory, so if I run this as if I'm in the US it works:

alter session set nls_territory = 'AMERICA';

select to_char(sysdate, 'D') as d, to_char(sysdate, 'Day') as day from dual;

D DAY
- ------------------------------------
6 Friday

select level as dow,
    to_char(trunc(sysdate ,'D') + level, 'Day') as day
from dual
connect by level <= 7;

DOW DAY
--- ------------------------------------
  1 Monday
  2 Tuesday
  3 Wednesday
  4 Thursday
  5 Friday
  6 Saturday
  7 Sunday

But the same query run in the UK is a day off:

alter session set nls_territory = 'UNITED KINGDOM';

select to_char(sysdate, 'D') as d, to_char(sysdate, 'Day') as day from dual;

D DAY
- ------------------------------------
5 Friday

select level as dow,
    to_char(trunc(sysdate ,'D') + level, 'Day') as day
from dual
connect by level <= 7;

DOW DAY
--- ------------------------------------
  1 Tuesday
  2 Wednesday
  3 Thursday
  4 Friday
  5 Saturday
  6 Sunday
  7 Monday

... and I need to adjust the calculation to correct for that:

select level as dow,
    to_char(trunc(sysdate ,'D') + level - 1, 'Day') as day
from dual
connect by level <= 7;

DOW DAY
--- ------------------------------------
  1 Monday
  2 Tuesday
  3 Wednesday
  4 Thursday
  5 Friday
  6 Saturday
  7 Sunday

You can also specify the language used for the day names separately if you want:

select level as dow,
    to_char(trunc(sysdate ,'day') + level - 1, 'Day',
        'NLS_DATE_LANGUAGE=FRENCH') as day
from dual
connect by level <= 7;

DOW DAY
--- --------------------------------
  1 Lundi
  2 Mardi
  3 Mercredi
  4 Jeudi
  5 Vendredi
  6 Samedi
  7 Dimanche

Documentation for to_char() with nls_date_language and day of the week, and more in the globalisation support guide.

Using Oracle SQL, how does one output day number of week and day of week?

4 Answers