Generate a range of dates using SQL

Question

I have a SQL query that takes a date parameter (if I were to throw it into a function) and I need to run it on every day of the last year.

How to generate a list of

Answer 1

A week from 6 months back

SELECT (date'2015-08-03' + (LEVEL-1)) AS DATES
 FROM DUAL 
 where ROWNUM < 8
 connect by level <= (sysdate-date'2015-08-03'); 

if you omit ROWNUM you get 50 rows only, independent of the value.

Answer 2

For the fun of it, here's some code that should work in SQL Server, Oracle, or MySQL:

SELECT current_timestamp - CAST(d1.digit + d2.digit + d3.digit as int)
FROM 
(
    SELECT digit
    FROM
    (
        select '1' as digit
        union select '2'
        union select '3'
        union select '4'
        union select '5'
        union select '6'
        union select '7'
        union select '8'
        union select '9'
        union select '0'
    ) digits
) d1
CROSS JOIN
(
    SELECT digit
    FROM
    (
        select '1' as digit
        union select '2'
        union select '3'
        union select '4'
        union select '5'
        union select '6'
        union select '7'
        union select '8'
        union select '9'
        union select '0'
    ) digits
) d2
CROSS JOIN
(
    SELECT digit
    FROM
    (
        select '1' as digit
        union select '2'
        union select '3'
        union select '4'
        union select '5'
        union select '6'
        union select '7'
        union select '8'
        union select '9'
        union select '0'
    ) digits
) d3
WHERE CAST(d1.digit + d2.digit + d3.digit as int) < 365
ORDER BY d1.digit, d2.digit, d3.digit -- order not really needed here

Bonus points if you can give me a cross-platform syntax to re-use the digits table.

Answer 3

Date range between 12/31/1996 and 12/31/2020

SELECT dt, to_char(dt, 'MM/DD/YYYY') as date_name, 
  EXTRACT(year from dt) as year, 
  EXTRACT(year from fiscal_dt) as fiscal_year,
  initcap(to_char(dt, 'MON')) as month,
  to_char(dt, 'YYYY')        || ' ' || initcap(to_char(dt, 'MON')) as year_month,
  to_char(fiscal_dt, 'YYYY') || ' ' || initcap(to_char(dt, 'MON')) as fiscal_year_month,
  EXTRACT(year from dt)*100        + EXTRACT(month from dt) as year_month_id,
  EXTRACT(year from fiscal_dt)*100 + EXTRACT(month from fiscal_dt) as fiscal_year_month_id,
  to_char(dt, 'YYYY')        || ' Q' || to_char(dt, 'Q') as quarter,
  to_char(fiscal_dt, 'YYYY') || ' Q' || to_char(fiscal_dt, 'Q') as fiscal_quarter
  --, EXTRACT(day from dt) as day_of_month, to_char(dt, 'YYYY-WW') as week_of_year, to_char(dt, 'D') as day_of_week
  FROM (
    SELECT dt, add_months(dt, 6) as fiscal_dt --starts July 1st
    FROM (
      SELECT TO_DATE('12/31/1996', 'mm/dd/yyyy') + ROWNUM as dt 
      FROM DUAL CONNECT BY ROWNUM < 366 * 30 --30 years
    )
    WHERE dt <= TO_DATE('12/31/2020', 'mm/dd/yyyy')
  )