SQL: Optimize query with multiple CASE statements - sql

Question

I have a query with many CASE statements that runs for a very long time due to the number of rows. In my research I have not found a solution yet. Is there a way to write the CASE statements more efficiently and with better performance?
database: Oracle
table_a
table
table_y
are all the same table where I SELECT from.
example data
contract_number
product_description
product
damagenumber
date
internalname
payment
1
Product T-Shirt
product_name
111
20210101
Web
30.20
2
Product T-Shirt
product_name
222
20210202
Web
19.38
3
Product Hoodie
product_name2
333
20210215
Store
20.49
3
Product Hoodie
product_name2
334
20210302
Store
15.99
5
Product Hoodie
product_name2
123
20210120
Telephone
99.99
SELECT
contract_number,
product_description,
product,
CASE
WHEN ( x.produkt = 'product_name'
AND (
SELECT
COUNT(DISTINCT damagenumber)
FROM
table z
WHERE
date BETWEEN add_months(trunc(sysdate), - 6) AND sysdate
AND internalname <> 'CONDITION'
AND x.contract_number = z.contract_number
GROUP BY
z.contract_number
) = 1
AND (
SELECT
SUM(y.payment)
FROM
table_y y
WHERE
date BETWEEN add_months(trunc(sysdate), - 6) AND sysdate
AND internalname <> 'CONDITION'
AND x.contract_number = y.contract_number
) > 1500 ) THEN
(
SELECT
COUNT(DISTINCT damagenumber)
FROM
table z
WHERE
date BETWEEN add_months(trunc(sysdate), - 6) AND sysdate
AND internalname <> 'CONDITION'
AND x.contract_number = z.contract_number
GROUP BY
z.contract_number
)
ELSE
0
END) AS count_numbers,
FROM
table_a x
GROUP BY
x.contract_number,
x.product_description,
x.product;
The above is a simplified example. I have a lot of WHEN conditions in my query.
Thanks in advance

Answer 1

maybe this help
with tabletemp as (
SELECT z.contract_number
, COUNT(DISTINCT damagenumber) damagenumber_count
FROM table z
WHERE date BETWEEN add_months(trunc(sysdate), - 6) AND sysdate AND internalname <> 'CONDITION'
GROUP BY z.contract_number
), tabletemp2 as (
SELECT y.contract_number
, SUM(y.payment) payment_sum
FROM table_y y
WHERE date BETWEEN add_months(trunc(sysdate), - 6) AND sysdate AND internalname <> 'CONDITION'
group by y.contract_number
)
SELECT
contract_number,
product_description,
product,
CASE WHEN ( x.produkt = 'product_name' AND tt.damagenumber_count = 1 AND tt2.payment_sum > 1500 ) THEN
tt.damagenumber_count
ELSE
0
END AS count_numbers,
FROM
table_a x
join tabletemp tt on (tt.contract_number = x.contract_number)
join tabletemp2 tt2 on (tt2.contract_number = x.contract_number)
Maybe this query have some errors (I can't test) but you should try this way