Combine 2 SQL queries into one - show gross & net sales - php

Question

I have the following two queries - one showing gross sales and one showing paid sales (the only difference between the queries is an added condition - flag_payment = 1).
The output is two columns - Supplier Name and then Gross or Paid Sales in $ (gross - query #1, paid - query #2). If possible, I would like to combine the two queries so that the output will be Supplier Name, Gross Sales and Paid Sales (i.e. 3 columns).
Query 1: Gross Sales
SELECT C.value , SUM( SL.price )
FROM sales_listings SL
INNER JOIN sales S ON SL.sale_id = S.id
INNER JOIN custom_fields_data C ON SL.listing_id = C.owner_id
WHERE C.field_id =11
GROUP BY C.value
Query 2: Paid Sales
SELECT C.value , SUM( SL.price )
FROM sales_listings SL
INNER JOIN sales S ON SL.sale_id = S.id
INNER JOIN custom_fields_data C ON SL.listing_id = C.owner_id
WHERE S.flag_payment = 1 AND C.field_id =11
GROUP BY C.value
Is there a way to combine the following two queries? Thank you!

Answer 1

You can use conditional aggregation:
SELECT
c.value,
SUM(CASE WHEN s.flag_payment = 0 THEN sl.price ELSE 0 END) AS GrossSales,
SUM(CASE WHEN s.flag_payment = 1 THEN sl.price ELSE 0 END) AS PaidSales
FROM sales_listings sl
INNER JOIN sales s
ON sl.sale_id = s.id
INNER JOIN custom_fields_data c
ON sl.listing_id = c.owner_id
WHERE
c.field_id = 11
GROUP BY c.value
Since in your original query for the Gross Sales, there is no filter for s.flag_payment, you can omit the conditional SUM:
SELECT
c.value,
SUM(sl.price) AS GrossSales,
SUM(CASE WHEN s.flag_payment = 1 THEN sl.price ELSE 0 END) AS PaidSales
FROM sales_listings sl
INNER JOIN sales s
ON sl.sale_id = s.id
INNER JOIN custom_fields_data c
ON sl.listing_id = c.owner_id
WHERE
c.field_id = 11
GROUP BY c.value