I have two tables exam_table and emp_table, Here i would like to join both tables using left outer join and I want to create a new column called new_column using exam_completed_date column from the right table.
x
select id, exam_completed_date from exam_table;
id exam_completed_date
0 12-01-2019
1 12-12-2019
select id, week_end_date from emp_table where id=0;
id week_end_date
0 11-29-2019
0 11-30-2019
0 12-31-2019
0 12-01-2019
0 12-02-2019
0 12-03-2019
0 12-04-2019
select id, week_end_date, exam_completed_date
from emp_table emp left outer join
exam_table exam
on (exam.id=emp.id and exam.exam_completed_date=emp.week_end_date)
where id=0
id week_end_date exam_completed_date
0 11-29-2019
0 11-30-2019
0 12-31-2019
0 12-01-2019 12-01-2019
0 12-02-2019
0 12-03-2019
0 12-04-2019
I need output like this
id week_end_date exam_completed_date new_column
0 11-29-2019
0 11-30-2019
0 12-31-2019
0 12-01-2019 12-01-2019 12-01-2019
0 12-02-2019 12-01-2019
0 12-03-2019 12-01-2019
0 12-04-2019 12-01-2019
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Answer
I think you want a cumulative max window function:
select id, week_end_date, exam_completed_date,
max(exam_completed_date) over (partition by id order by week_end_date) as newcolumn
from emp_table emp left outer join
exam_table exam
on exam.id=emp.id and
exam.exam_completed_date = emp.week_end_date
where id = 0;