如何从预定义的日期表（Oracle SQL）中获取每周的最后一个日期和第一个日期

Question

I have Table D_date in which all dates of a year, week number,quarter number etc attributes are defined. I just want to get first and last date of every week of year 2015.

Sample D_date tabe attached.

Answer 1

It is simple min/max if I understand you right

SELECT calendar_year_nbr, week, min(actual_date),max(actual_date)
FROM D_date
GROUP BY calendar_year_nbr, week

Answer 2

I just want to get first and last date of every week of year 2015.

Since you have precomputed values already stored in the table, you could directly use MIN and MAX as aggregate functions along with GROUP BY .

For example,

SELECT MIN(actual_date) min_date,
      MAX(actual_date) max_date,
      calendar_week_nbr
FROM d_date
WHERE calendar_year_nbr = 2015
GROUP BY calendar_week_nbr
ORDER BY min_date;

Another way is to use ROWNUM() OVER() analytic function.