MySQL which query statement should be used? - mysql

Question

I have a dataset like this as shown below, for example row 1, 0 purchase is made for the item priced at $3, 3 purchases are made for item priced at $30. I would need to write a query to provide the summary of how many passes purchased, by categorising the prices into price range of "0-10", "11-20", "21-30", "31-40". I assume case when should be used but I am unsure of how. Please help.
+-----------------+-----------------+--------------------------+--------------------------+
| price_category1 | price_category2 | purchase_count_category1 | purchase_count_category2 |
+-----------------+-----------------+--------------------------+--------------------------+
| 3 | 30 | 0 | 3 |
| 20 | 6 | 1 | 4 |
| 25 | 11 | 4 | 0 |
| 17 | 12 | 0 | 1 |
+-----------------+-----------------+--------------------------+--------------------------+
+------+-------+-------+-------+
| 0-10 | 11-20 | 21-30 | 31-40 |
+------+-------+-------+-------+
| 4 | 2 | 7 | 0 |
+------+-------+-------+-------+

Answer 1

You can try below.
Working Solution
WITH MAIN
AS (SELECT 3 AS price_category1,
30 AS price_category2,
0 purchase_count_category1,
3 AS purchase_count_category2
FROM DUAL
UNION ALL
SELECT 20 AS price_category1,
6 AS price_category2,
1 purchase_count_category1,
4 AS purchase_count_category2
FROM DUAL
UNION ALL
SELECT 25 AS price_category1,
11 AS price_category2,
4 purchase_count_category1,
0 AS purchase_count_category2
FROM DUAL
UNION ALL
SELECT 17 AS price_category1,
12 AS price_category2,
0 purchase_count_category1,
1 AS purchase_count_category2
FROM DUAL),
M2
AS (SELECT price_category1 CAT, purchase_count_category1 CNT FROM MAIN
UNION
SELECT price_category2, purchase_count_category2 FROM MAIN)
SELECT CASE
WHEN CAT >= 0 AND CAT < 11 THEN '0-10'
WHEN CAT >= 11 AND CAT < 21 THEN '11-20'
WHEN CAT >= 21 AND CAT < 31 THEN '21-30'
END
CAT,
SUM (CNT) SUMM
FROM M2
GROUP BY CASE
WHEN CAT >= 0 AND CAT < 11 THEN '0-10'
WHEN CAT >= 11 AND CAT < 21 THEN '11-20'
WHEN CAT >= 21 AND CAT < 31 THEN '21-30'
END

Answer 2

SELECT SUM(CASE WHEN price_category1 BETWEEN 0 AND 10
THEN purchase_count_category1
END) + SUM(CASE WHEN price_category2 BETWEEN 0 AND 10
THEN purchase_count_category2
END) AS `0-10`,
SUM(CASE WHEN price_category1 BETWEEN 11 AND 20
THEN purchase_count_category1
END) + SUM(CASE WHEN price_category2 BETWEEN 11 AND 20
THEN purchase_count_category2
END) AS `11-20`,
SUM(CASE WHEN price_category1 BETWEEN 21 AND 30
THEN purchase_count_category1
END) + SUM(CASE WHEN price_category2 BETWEEN 21 AND 30
THEN purchase_count_category2
END) AS `21-30`
FROM source_table
or
SELECT SUM(CASE WHEN cat BETWEEN 0 AND 10
THEN cnt
END ) AS `0-10`,
SUM(CASE WHEN cat BETWEEN 11 AND 20
THEN cnt
END ) AS `11-20`,
SUM(CASE WHEN cat BETWEEN 21 AND 30
THEN cnt
END ) AS `21-30`
FROM ( SELECT price_category1 cat, purchase_count_category1 cnt
FROM source_table
UNION ALL
SELECT price_category2, purchase_count_category2
FROM source_table ) src
PS. This solution gives "horizontal" output - one row with all needed statistic. If you need "vertical" output then use the solution provided by ismetguzelgun.
Pay attention - my solution is not extendable (if you need to alter the ranges amount or borders you must alter the query text) whereas alternative solution can be extended easily after converting hardcoded ranges borders to according CTE or (the best) additional criteria table.