How Can I Generate Dates Across Multiple Date Ranges in Oracle?

Handling Multiple Date Ranges for Date Generation

Generating dates between two dates is commonly encountered in various programming scenarios. While generating dates for a single range is straightforward, extending this functionality to handle multiple ranges can pose challenges.

Consider the following table where each row represents a date range:

ID	START_DATE	END_DATE
101	April 1, 2013	April 10, 2013
102	May 10, 2013	May 12, 2013

The expected output should generate individual dates within each range:

ID	Dates
101	April 1, 2013
101	April 2, 2013
...	...
101	April 10, 2013
102	May 10, 2013
102	May 11, 2013
102	May 12, 2013

Oracle provides an ingenious solution to achieve this result:

select 
  A.ID, 
  A.START_DATE + (delta - 1) dt
from 
  t_dates A, 
  (
     select level-1 as delta 
     from dual 
     connect by level-1 <= (
       select max(end_date - start_date) from t_dates
     )
  )
where A.START_DATE + (delta - 1) <= A.end_date
order by 1, 2;

The delta column employs Oracle's CONNECT BY hierarchy to generate a sequence of integers from 1 up to the maximum difference between end and start dates in the table. The A.START_DATE (delta - 1) expression increments the start date by the appropriate delta for each record in the results. The WHERE clause filters out results that exceed the current date range's end date.

Enjoy this elegant solution for generating dates across multiple ranges in Oracle!

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