在SQL Postgres中按组进行迭代

Question

Starting with the end goal, I want a result set looking like the following:

name  | completed
_________________
Josh  |  T
Tom   |  T
Harry |  F

I have a table that looks like:

id | name | status
__________________
1    Josh   complete
2    Josh   errored
3    Tom    generating
4    Tom    complete
5    Harry  pending

As you can see from the result set, I want to know for each person whether they have ever had a status of complete. I think I want to iterate over each row in the grouped by clause checking status = 'complete' but I am struggling to do so.

Answer 1

You can do aggregation :

select name, coalesce(max(case when status = 'complete' then T end), 'F') as completed
from table t
group by name;

Answer 2

You could use the bool_or aggregate function :

SELECT name, bool_or(status = 'complete')
FROM test
GROUP BY name

yields

| name  | bool_or |
|-------+---------|
| Tom   | t       |
| Josh  | t       |
| Harry | f       |