How to include values that count nothing on certain day (APEX) - sql

Question

I have this query:
SELECT
COUNT(ID) AS FREQ,
TO_CHAR(TRUNC(CREATED_AT),'DD-MON') DATES
FROM TICKETS
WHERE TRUNC(CREATED_AT) > TRUNC(SYSDATE) - 32
GROUP BY TRUNC(CREATED_AT)
ORDER BY TRUNC(CREATED_AT) ASC
This counts how many tickets where created every day for the past month.
The result looks something like this: (first 10 rows)
FREQ DATES
3 28-DEC
4 04-JAN
8 05-JAN
1 06-JAN
4 07-JAN
5 08-JAN
2 11-JAN
6 12-JAN
3 13-JAN
8 14-JAN
The linechart that I created looks like this:
The problem is that the days where tickets are not created (in particular the weekends) the line just goes straight to the day where there is created a ticket.
Is there a way in APEX or in my query to include the days that aren't counted?

Answer 1

As commented, using one of row generator techniques you'd create a "calendar" table and outer join it with a table that contains data you're displaying.
Something like this (see comments within code):
SQL> with yours (amount, datum) as
2 -- your sample table
3 (select 100, date '2021-01-01' from dual union all
4 select 200, date '2021-01-03' from dual union all
5 select 300, date '2021-01-07' from dual
6 ),
7 minimax as
8 -- MIN and MAX date (so that they could be used in row generator --> CALENDAR CTE (below)
9 (select min(datum) min_datum,
10 max(datum) max_datum
11 from yours
12 ),
13 calendar as
14 -- calendar, from MIN to MAX date in YOUR table
15 (select min_datum + level - 1 datum
16 from minimax
17 connect by level <= max_datum - min_datum + 1
18 )
19 -- final query uses outer join
20 select c.datum,
21 nvl(y.amount, 0) amount
22 from calendar c left join yours y on y.datum = c.datum
23 order by c.datum;
DATUM AMOUNT
---------- ----------
01.01.2021 100
02.01.2021 0
03.01.2021 200
04.01.2021 0
05.01.2021 0
06.01.2021 0
07.01.2021 300
7 rows selected.
SQL>
Applied to your current query:
WITH
minimax
AS
-- MIN and MAX date (so that they could be used in row generator --> CALENDAR CTE (below)
(SELECT MIN (created_at) min_datum, MAX (created_at) max_datum
FROM tickets),
calendar
AS
-- calendar, from MIN to MAX date in YOUR table
( SELECT min_datum + LEVEL - 1 datum
FROM minimax
CONNECT BY LEVEL <= max_datum - min_datum + 1)
-- final query uses outer join
SELECT COUNT (t.id) AS freq, TO_CHAR (TRUNC (c.datum), 'DD-MON') dates
FROM calendar c LEFT JOIN tickets t ON t.created_at = c.datum
WHERE TRUNC (t.created_at) > TRUNC (SYSDATE) - 32
GROUP BY TRUNC (c.datum)
ORDER BY dates ASC

Answer 2

I added a with clause to generate last 31 days, then I left joined with your base table like below.
with last_31_days as (
select trunc(sysdate) - 32 + level dt from dual connect by trunc(sysdate) - 32 + level < trunc(sysdate)
)
SELECT
nvl(COUNT(t.ID), 0) AS FREQ,
TO_CHAR(
nvl(TRUNC(t.CREATED_AT), a.dt)
,'DD-MON') DATES
FROM last_31_days a
LEFT JOIN TICKETS t
ON TRUNC(t.CREATED_AT) = a.dt
GROUP BY nvl(TRUNC(t.CREATED_AT), a.dt)
ORDER BY 2 ASC
;

Answer 3

#Littlefoot answer is perfect. but here is a cheeky way to get the similar table with format match OP output. using a simple cte for this.
WITH cte AS (
SELECT To_Char(Trunc(SYSDATE - ROWNUM),'DD-MON') dtcol
FROM DUAL
CONNECT BY ROWNUM < 366
)
SELECT * FROM cte
here is db<>fiddle
and then you can simply join this cte to fill up empty date. as the origin output column date looks like a string column.
connect by is for oracle only. but I think you can still use recursive cte to get similar result in other DBMS support recursive cte.