JOIN two tables and GROUP by the common column [duplicate] - mysql

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MySQL Results as comma separated list
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Closed 5 years ago.
I'm new to MYSQL and struggling to form a query that joins two tables and returns a unique product row.
TABLE product:
╔══════════════════════════════╦══════════╦════════════╦════════════════════╗
║ ref ║ brand ║ mpn ║ sku ║
╠══════════════════════════════╬══════════╬════════════╬════════════════════╣
║ 0001___DOGICLON___912-101242 ║ DOGICLON ║ 912-101242 ║ 000000000001082649 ║
║ 0002___DOGICLON___912-101242 ║ DOGICLON ║ 912-101242 ║ 912-101242 ║
║ 0003___Dogiclon___912-101242 ║ Dogiclon ║ 912-101242 ║ 912-101242(R400) ║
║ 0005___Dogiclon___912-101242 ║ Dogiclon ║ 912-101242 ║ MILT-R400 ║
╚══════════════════════════════╩══════════╩════════════╩════════════════════╝
TABLE inventory:
╔══════════════════════════════╦═══════╦═════════╦══════════╗
║ ref ║ scost ║ instock ║ location ║
╠══════════════════════════════╬═══════╬═════════╬══════════╣
║ 0001___DOGICLON___912-101242 ║ 53.68 ║ 24 ║ WA ║
║ 0001___DOGICLON___912-101242 ║ 53.68 ║ 0 ║ CA ║
║ 0002___DOGICLON___912-101242 ║ 61.00 ║ 121 ║ WA ║
║ 0003___Dogiclon___912-101242 ║ 53.53 ║ 100 ║ WA ║
║ 0003___Dogiclon___912-101242 ║ 53.53 ║ 0 ║ NY ║
║ 0003___Dogiclon___912-101242 ║ 53.53 ║ 20 ║ MA ║
║ 0003___Dogiclon___912-101242 ║ 53.53 ║ 2 ║ CA ║
║ 0005___Dogiclon___912-101242 ║ 56.00 ║ 5 ║ IN ║
║ 0005___Dogiclon___912-101242 ║ 56.00 ║ 5 ║ MA ║
║ 0005___Dogiclon___912-101242 ║ 56.00 ║ 5 ║ WA ║
║ 0005___Dogiclon___912-101242 ║ 56.00 ║ 5 ║ NY ║
║ 0005___Dogiclon___912-101242 ║ 56.00 ║ 2 ║ CA ║
╚══════════════════════════════╩═══════╩═════════╩══════════╝
I guess pseduo code would be:
SHOW all products
WHERE
instock (any location) > 0 AND
(cost > 10 AND cost < 2000)
ORDER BY
cost asc
Notes:
refs are unique per supplier
brand and mpn lookup needs to be
case insensitive
Expected Result:
╔══════════╦══════════╦════════════╦══════════════╦══════════════╦═══════════════════════════╗
║ ref ║ brand ║ mpn ║ sku ║ scost ║ instock ║
╠══════════╬══════════╬════════════╬══════════════╬══════════════╬═══════════════════════════╣
║ whatever ║ Dogiclon ║ 912-101242 ║ based on ref ║ based on ref ║ based on ref and location ║
╚══════════╩══════════╩════════════╩══════════════╩══════════════╩═══════════════════════════╝
This is what I'm trying:
SELECT DISTINCT
product.ref,
product.brand,
inventory.scost,
inventory.instock
FROM
product
JOIN inventory ON inventory.ref = product.ref
WHERE
inventory.instock > 1
AND ( app.inventory.scost >= 10 AND app.inventory.scost <= 2000 )
GROUP BY
product.ref

Answer 1

If you are grouping by unique column within product which seems to be ref, distinct won't do what you wish it would. DISTINCT takes care of uniqueness per returned row (all values being returned). In this case to get one row in result per product ref you'd need to drop the distinct part, add product.mfr to group by and aggregate non-grouped columns like below:
SELECT
product.ref,
product.mfr,
group_concat(inventory.scost) as scost,
group_concat(inventory.instock) as instock,
FROM
product
JOIN inventory ON inventory.ref = product.ref
WHERE
inventory.instock > 1
AND ( app.inventory.scost >= 10 AND app.inventory.scost <= 2000 )
GROUP BY
product.ref, product.mfr
If you want to ensure proper ordering for scost and instock just include ordering clause within the group_concat itself ie:
group_concat(column order by column1, [...])