Variables Declaration, CTEs, and While Loops in Oracle SQL - sql

Question

So I might be stuck at something very trivial but can't figure out how to make it work. I create a 2 blocks of code that work in SQL but I have some problems with the date variable declaration in Oracle SQL.
I had write access to the SQL database when I create these codes so I did a 'Insert Into' to create temp tables. I don't have write access anymore. So I am using CTEs for it.
The original code looks like this:
DECLARE #Startdate Datetime = '2021-Jun-01 00:00:00.000'
DECLARE #Enddate Datetime = '2021-Jun-30 00:00:00.000'
Insert into Temp1
select ...
from ...
WHILE Startdate <= Enddate
BEGIN
Insert into Temp2
select ...
from (Temp 1)
left join
select ...
set #startdate=dateadd(d,1,#startdate)
end;
With my new code, I have made the following adjustmnets:
VARIABLE Startdate Datetime = '2021-Jun-01 00:00:00.000'
VARIABLE Enddate Datetime = '2021-Jun-30 00:00:00.000'
EXEC :Startdate := '2021-Jun-30 00:00:00.000'
EXEC :Enddate := '2021-Jun-30 00:00:00.000'
WITH Temp1 as (
select ...
from ...),
/* Unsure about using WHILE with with 2 CTEs so removing them for now but will need to be added*/
WITH Temp2 as
select ...
from (Temp 1)
left join
select ...
set startdate = :startdate + 1
end)
select * from Temp2;
The 2 blocks of code work perfectly individually. I think my concern lies with one or all of the following:
Variable Declaration - I read a couple of stackoverflow posts and it seems like there is binding variable and substitution variable. Is there a different way to declare variables?
The WHILE Loop specially between 2 CTEs. Can we do a while loop as a CTE? (similar to this) create while loop with cte
How the date is incremented. Is this the proper way to increment dates in Oracle PL/SQL?
Any guidance would be helpful.
Also adding 2 blocks of codes for reference:
Details of Tables:
Transactions - Contains Transaction information. Execution Date is a timestamp of the transaction execution
Account - Contains Account Information with a unique Account_Key for every account
Code_Rel - Maps the transaction code to a transaction type
Group Rel - Maps the transaction type to a transaction group
/***Block 1 of Code***/
insert into Temp1
select
a.ACCOUNT_KEY
,a.SPG_CD
,t.EXECUTION_DATE
from Schema_Name.TRANSACTIONS t
inner join Schema_Name.ACCOUNT a on a.en_sk=t.ac_sk
inner join Schema_Name.Code_Rel tr on t.t_cd_s = tr.t_cd_s
inner join ( select * from Schema_Name.Group_Rel
where gtrt_cd in ('Type1','Type2')) tt on tr.trt_cd = tt.trt_cd
where t.EXECUTION_DATE >= #startdate and t.EXECUTION_DATE<=#EndDt
and tt.gtrt_cd in ('Type1','Type2')
group by a.ACCOUNT_KEY ,a.SPG_CD, t.EXECUTION_DATE;
/***WHILE LOOP***/
while #startdate <= #EndDt
BEGIN
/***INSERT AND BLOCK 2 OF CODE***/
insert into Temp2
select table1.account_key, table1.SPG_CD, #startdate, coalesce(table2.sum_tr1,0),coalesce(table3.sum_tr2,0),
case when coalesce(table3.sum_tr2,0)>0 THEN coalesce(table2.sum_tr1,0)/coalesce(table3.sum_tr2,0) ELSE 0 END,
case when coalesce(table3.sum_tr2,0)>0 THEN
CASE WHEN coalesce(table2.sum_tr1,0)/coalesce(table3.sum_tr2,0)>=0.9 and coalesce(table2.sum_tr1,0)/coalesce(table3.sum_tr2,0)<=1.10 and coalesce(table2.sum_tr1,0)>=1000 THEN 'Yes' else 'No' END
ELSE 'No' END
FROM ( SELECT * FROM Temp1 WHERE execution_date=#startdate) TABLE1 LEFT JOIN
(
select a.account_key,a.SPG_CD, SUM(t.AC_Amt) as sum_tr1
from Schema_Name.TRANSACTIONS t
inner join Schema_Name.ACCOUNT a on a.en_sk=t.ac_sk
inner join Schema_Name.Code_Rel tr on t.t_cd_s = tr.t_cd_s
inner join ( select * from Schema_Name.Group_Rel
where gtrt_cd in ('Type1')) tt on tr.trt_cd = tt.trt_cd
where t.EXECUTION_DATE <= #startdate
and t.EXECUTION_DATE >=dateadd(day,-6,#startdate)
and tt.gtrt_cd in ('Type1')
group by a.account_key, a.SPG_CD
) table2 ON table1.account_key=table2.account_key
LEFT JOIN
(
select a.account_key,a.SPG_CD, SUM(t.AC_Amt) as sum_tr2
from Schema_Name.TRANSACTIONS t
inner join Schema_Name.ACCOUNT a on a.en_sk=t.ac_sk
inner join Schema_Name.Code_Rel tr on t.t_cd_s = tr.t_cd_s
inner join ( select * from Schema_Name.Group_Rel
where gtrt_cd in ('Type2')) tt on tr.trt_cd = tt.trt_cd
where t.EXECUTION_DATE <= #startdate
and t.EXECUTION_DATE >=dateadd(day,-6,#startdate)
and tt.gtrt_cd in ('Type2')
group by a.account_key, a.SPG_CD ) table3 on table1.account_key=table3.account_key
where coalesce(table2.sum_tr1,0)>=1000
set #startdate=dateadd(d,1,#startdate)
end;

Answer 1

You do not need to use PL/SQL or a WHILE loop or to declare variables and can probably do it all in a single SQL query using subquery factoring clauses (and recursion) to generate a calendar of incrementing dates. Something like this made-up example:
INSERT INTO temp2 (col1, col2, col3)
WITH time_bounds(start_date, end_date) AS (
-- You can declare the bounds in the query.
SELECT DATE '2021-06-01',
DATE '2021-06-30'
FROM DUAL
),
calendar (dt, end_date) AS (
-- Recursive query to generate a row for each day.
SELECT start_date, end_date FROM time_bounds
UNION ALL
SELECT dt + INTERVAL '1' DAY, end_date
FROM calendar
WHERE dt + INTERVAL '1' DAY <= end_date
),
temp1 (a, b, c) AS (
-- Made-up query
SELECT a, b, c FROM some_table
),
temp2 (a, d, e) AS (
-- Another made-up query.
SELECT t1.a,
s2.d,
s2.e
FROM temp1 t1
LEFT OUTER JOIN some_other_table s2
ON (t1.b = s2.b)
)
-- Get the values to insert.
SELECT t2.a,
t2.d,
t2.e
FROM temp2 t2
INNER JOIN calendar c
ON (t2.e = c.dt)
WHERE a BETWEEN 3.14159 AND 42;
If you try doing it with multiple inserts in a PL/SQL loop then it will be much slower than a single statement.