DB2 How to convert the following "with temp as" into a normal select statement - db2

Question

I'm trying to do an insert with this "with" statement but it seems like it supports select statement only, therefore I want to convert it into select statement. I'm just amazed on how this is working. Got a similar example on stack and changed it to fit my needs.
with temp (startdate, enddate, maxdate) as (
select min(salesdate) startdate, min(salesdate)+3 months enddate, max(salesdate) maxdate
from SALES
union all
select startdate + 3 months + 1 days, enddate + 3 months + 1 days, maxdate from temp
where enddate <= maxdate
)
select startdate, min(enddate, maxdate) from temp;
Thanks in advance.
Edit: It seems my query is misunderstood. Here is the pseudo code of what the query is supposed to be doing. The query is returning the expected result which is pretty amazing to me. I don't know how the recursive doesn't overlap after I added 1 day. After writing the pseudo code, I see that the select startdate + 3 months + 1 days should have been written as select enddate + 1 days which logically says what it's supposed to do instead of magically work:
rows = []
startdate = min(salesdate)
enddate = startdate + 3 months
maxdate = max(salesdate)
i = 0;
do {
rows[i++] = [startdate, min(enddate, maxdate)] // min for final iteration where enddate > maxdate.
startdate = enddate + 1 days
enddate = enddate + 1 days + 3 months // aka: startdate + 3 months
} while (enddate <= maxdate)
return rows
Hence, I've broken a huge date range into smaller chunks of 3 months ranges. Whether it is exactly 90 days or 91 days is not important, as long as I get every single date without gap and without overlap.

Answer 1

I'm curious about your decision, that a query with a recursive common table expression (RCTE) is "not normal". IBM calls it as 'select-statement' and considers it as normal. If it's some educational question, and you don't want to use RCTE due to some reason, then consider the the following example.
select s + (3*(x.i-1)) month start, s + (3*x.i) month - 1 day end
from table(values (date('2011-01-01'), date('2012-01-01'))) d(s, e)
, xmltable('for $id in (1 to $e) return <i>{number($id)}</i>'
passing ((year(e)-year(s))*12 + (month(e)-month(s)))/3 as "e"
columns i int path '.'
) x;
START END
---------- ----------
2011-01-01 2011-03-31
2011-04-01 2011-06-30
2011-07-01 2011-09-30
2011-10-01 2011-12-31
;
It's a little bit complicated, since you must pass desired number of rows to return to the xmltable table function, which returns a single column with values 1 to N. In other words you must compute desired number of 3-months intervals and pass it to the function.
(R)CTE can't be used in the UPDATE/DELETE statements, where you are able to use so called fullselect statements only (they don't allow CTEs). If you really need to use CTE for UPDATE/DELETE as in this case, you can do one of the following:
If you ARE ABLE to compute a temporary result set for whole delete/update statement, you can do something like this (I don't use here RCTE for simplicity, but a simple CTE only):
with a (id) as (values 1)
select count(1)
from old table(
delete from test t
where exists (select 1 from a where a.id=t.id)
);
If you ARE NOT ABLE to compute a temporary result set for whole delete/update statement, you can create a table/scalar function with the corresponding parameters, where you are able to use your RCTE. This function can be used in the outer statement afterwards.

Answer 2

I was able to insert it by moving the insert statement in front of the "with" statement. Copying answer here so I know next time. Although, I'm still interested in seeing how to convert it to a pure select statement. Will select that answer as the correct answer.
insert into my_temp_table
with temp (startdate, enddate, maxdate) as (
select min(salesdate) startdate, min(salesdate)+3 months enddate, max(salesdate) maxdate
from SALES
union all
select startdate + 3 months + 1 days, enddate + 3 months + 1 days, maxdate from temp
where enddate <= maxdate
)
select startdate, min(enddate, maxdate) from temp;