Inserting Rows that don't exist and use previous value - mysql

Question

I am trying to insert rows that do not exist in the table that I am pulling from, it is sequenced by the days_to_cancel column and starts back at zero with a new Year/Month entry. I am using the following query:
CREATE TABLE reporting.tbl_exec_retention_curve_cumulative (days_to_cancel int, cancels int, cumulative_cancels int, enroll_dt varchar(50));
SELECT rc.days_to_cancel,
rc.cancels,
(#run_total := CASE WHEN rc.days_to_cancel <> 0 THEN #run_total +
rc.cancels ELSE rc.cancels END) AS cumulative_cancels,
LEFT(rc.client_enroll_dt,7) AS client_enroll_dt
FROM (SELECT rc.days_to_cancel,
SUM(CASE WHEN rc.client_status = 'CAN' THEN 1 ELSE 0 END) AS cancels,
LEFT(rc.client_enroll_dt,7) AS client_enroll_dt
FROM t1.table rc
GROUP BY 1,3
ORDER BY 3,1
) rc
JOIN (SELECT #run_total := 0) r
GROUP BY 1,4
ORDER BY 4,1;
I get a sample result of the following
days_to_cancel | cancels | cumulative_cancels | client_enroll_dt
---------------+---------+--------------------+------------------
42 | 2 | 376 | 2019-02
47 | 0 | 376 | 2019-02
0 | 0 | 0 | 2019-03
10 | 4 | 4 | 2019-03
11 | 9 | 13 | 2019-03
So my goal is to input the missing days and use the previous cumulative_cancels and enroll_dt values and 0 for the cancels column when I input that new row for those missing days. I've tried multiple ways including using variables, but I'm at a loss of what to do. I don't know if it's possible considering the rows never existed in the first place. If it matters I am on version 10.0.35 of MariaDB.

Answer 1

I just imagine that you fetched data from t1.table and want to insert your result into the same table.
My solution is putting your result into a temporary table then find the missing days by left join.
SELECT rc.days_to_cancel,
rc.cancels,
(#run_total := CASE WHEN rc.days_to_cancel <> 0 THEN #run_total +
rc.cancels ELSE rc.cancels END) AS cumulative_cancels,
LEFT(rc.client_enroll_dt,7) AS client_enroll_dt
--put your result into a temp table
into #temp
FROM (SELECT rc.days_to_cancel,
SUM(CASE WHEN rc.client_status = 'CAN' THEN 1 ELSE 0 END) AS cancels,
LEFT(rc.client_enroll_dt,7) AS client_enroll_dt
FROM t1.table rc
GROUP BY 1,3
ORDER BY 3,1
) rc
JOIN (SELECT #run_total := 0) r
GROUP BY 1,4
ORDER BY 4,1;
insert into t1.table (days_to_cancel, cancels,cumulative_cancels, client_enroll_dt)
select tm.days_to_cancel, tm.cancels, tm.cumulative_cancels, tm.client_enroll_d from #temp tm
left join t1.table rc on rc.days_to_cancel = tm.days_to_cancel
where rc.days_to_cancel is null --find out missing days
drop table #temp