How to order by the group by in mysql? - mysql

Question

I have the code below but i want to arrange it by date_available desc and group it by store_id so that i will only return 1 value.
SELECT
product_to_store.store_id,
product.date_available,
product.product_id,
product_description.name,
product_to_category.category_id,
pcd3.name,
lvl2.parent_id,
pcd2.name,
CASE
WHEN lvl2.parent_id > 0 THEN lvl1.parent_id
ELSE 0
END,
pcd1.name,
product.quantity,
product_type.type
FROM product
inner join product_to_store on (product.product_id=product_to_store.product_id)
inner join product_description on (product.product_id = product_description.product_id)
inner join product_to_category on (product.product_id = product_to_category.product_id)
inner join product_type on (product.product_id = product_type.product_id)
inner join store on (product_to_store.store_id = store.store_id)
inner join product_category as lvl2 on (product_to_category.category_id = lvl2.category_id)
inner join product_category as lvl1 on (lvl1.category_id = lvl2.parent_id)
inner join product_category_description as pcd3 on (pcd3.category_id = lvl2.category_id)
inner join product_category_description as pcd2 on (pcd2.category_id = lvl2.parent_id)
inner join product_category_description as pcd1 on (pcd1.category_id = lvl1.parent_id)
Sample table:
store_id date_available name
1 2017-05-04 T1
1 0000-00-00 T2
2 2017-06-04 T3
3 0000-00-00 T4
2 2017-04-04 T5
3 0000-00-00 T6
Expected result:
store_id date_available name
1 2017-05-04 T1
2 2017-06-04 T3
3 0000-00-00 T4
How can i do that in mysql? Please help me thank you.

Answer 1

Use this as a hint:
-- Create some testing data
IF OBJECT_ID('tempdb..#product') IS NOT NULL DROP TABLE #product
CREATE TABLE #product(
[store_id] int
,[date_available] varchar(50)
,[name] varchar(50)
)
INSERT INTO #product VALUES
(1, '2017-05-04', 'T1')
,(1, '0000-00-00', 'T2')
,(2, '2017-06-04', 'T3')
,(3, '0000-00-00', 'T4')
,(2, '2017-04-04', 'T5')
,(3, '0000-00-00', 'T6')
-- Get result
SELECT p1.[store_id], p1.[date_available], MIN(p2.[name]) AS [name]
FROM (
SELECT [store_id], MAX([date_available]) AS [date_available] FROM #product
GROUP BY [store_id]
) p1
INNER JOIN #product p2
ON p1.[store_id] = p2.[store_id] AND p1.[date_available] = p2.[date_available]
GROUP BY p1.[store_id], p1.[date_available]
-- Destroy the temp table
DROP TABLE #product
Then in your long script, you may rewrite it to something like this:
SELECT product_to_store.store_id,
product.date_available,
product.product_id,
.
.
.
FROM product
INNER JOIN ...
INNER JOIN ...
INNER JOIN (
SELECT p1.[store_id], p1.[date_available], MIN(p2.[name]) AS [name]
FROM (
SELECT [store_id], MAX([date_available]) AS [date_available] FROM #product
GROUP BY [store_id]
) p1
INNER JOIN #product p2
ON p1.[store_id] = p2.[store_id] AND p1.[date_available] = p2.[date_available]
GROUP BY p1.[store_id], p1.[date_available]
) store ON (product_to_store.store_id = store.store_id)
INNER JOIN ...
INNER JOIN ...