I have a query I cannot wrap my head around. Let's say I have this table, items with 6 records
item_id passage_id
========== ==========
6 0
5 3
4 0
3 0
2 3
1 3
To get the records by descending item_id, I run the statement SELECT * FROM items ORDER BY item_id DESC, and the result is simply the same as the source table above.
But now it gets tricky. I now want to sort by descending item_id, but if there are other items with the same passage_id, I want them grouped by that passage_id.
item_id passage_id
========== ==========
6 0
5 3
2 3
1 3
4 0
3 0
How can I do this in a single SQL statement? The order is crucial because I need preserve it even when a limit is used:
SELECT * FROM items ORDER BY ??? LIMIT 0, 3
item_id passage_id
========== ==========
6 0
5 3
2 3
SELECT * FROM items ORDER BY ??? LIMIT 2, 3
item_id passage_id
========== ==========
1 3
4 0
3 0
EDIT: Here's the answer, taken from Gordon Linoff's answer below
SELECT i.item_id, i.passage_id
FROM items i LEFT JOIN (
SELECT i.passage_id, MAX(i.item_id) AS imax_id
FROM items i
GROUP BY i.passage_id
) imax
ON i.passage_id = imax.passage_id
ORDER BY CASE WHEN i.passage_id=0 THEN i.item_id ELSE imax.imax_id END DESC, i.item_id DESC;
If I understand correctly, you want to do something like keep the passage_ids together and sort these groups by the item ids. The following should actually do this:
select i.item_id, i.passage_id
from items i join
(select i.passage_id, max(i.item_id) as maxiid
from items i
group by i.passage_id
) imax
on i.passage_id = i.passage_id
order by imax.maxiid,
i.item_id desc;
But, it will not produce your ordering, because of passage_id = 0. For these, you seem to want them based only on the item_id itself. So, I think this encapsulates your logic:
select i.item_id, i.passage_id
from items i join
(select i.passage_id, max(i.item_id) as maxiid
from items i
group by i.passage_id
) imax
on i.passage_id = i.passage_id
order by (case when i.passage_id = 0 then i.item_id else imax.maxiid end) desc,
i.item_id desc;
Related
i need a query that should first look the oldest order which has status 0 (zero). and retrieves all the similar orders of that kind(matches exact total qty, itemSku and number of distinct items ordered).
***OrdersTable***
ID OrderNumber CustomerId Status created_at
1 123456 1 0 2018-01-01
2 234567 1 0 2018-01-02
3 345678 1 0 2018-01-03
4 456789 1 0 2018-01-04
***PurchasedProductsTable***
OrderId itemSku Qty
1 1000001 1
1 1000002 2
2 1000001 3
3 1000001 1
3 1000002 2
4 1000001 3
In the above table the query should first look at the oldest (created_at ASC) order (i.e with Id 1) having status 0 (in order table). and along with that order it should retrieves all the other orders that matches the same itemSku, qty and total distinct items count (in purchasedProducts table).
here order 1 and 3 matches the same itemSKu (1000001 and 1000002) and qty ( 1 and 2) and both have (2) distinct items count respectively so order 1 and 3 should be retrived at first.and when i marked order 1 and 3 as shipped (i.e chang status to 2).
and if i run query again it should retrive similar oders. now order 2 and 4 as order 2 and 4 are similar orders. (have same itemSkus (1000001, Qty (3) and distinct items count (1)).
please help thanks
You have to go trough your tables two times :)
Something like this :
SELECT DISTINCT O2.ID
FROM OrdersTable O1
INNER JOIN PurchasedProductsTable P1 ON O1.ID = P1.OrderId
INNER JOIN PurchasedProductsTable P2 ON P1.itemSku = P2.itemSku
AND P1.Qty = P2.Qty
INNER JOIN OrdersTable O2 ON O2.ID = P2.OrderId
WHERE O1.ID =
(SELECT ID FROM OrdersTable WHERE Status = 0
ORDER BY created_at ASC LIMIT 1)
AND (SELECT COUNT(*) FROM PurchasedProductsTable WHERE OrderId = O1.ID)
= (SELECT COUNT(*) FROM PurchasedProductsTable WHERE OrderId = O2.ID)
ORDER BY O2.ID ASC;
https://www.db-fiddle.com/f/65t9GgSfqMpzNVgnrJp2TR/2
You can get the earliest order via a limit and ordered by the date.
Then you can left join to get that order and any other order that at least has the same items.
Then once you have those order id's from the sub-query result, you can get the order details.
SELECT o.*
FROM
(
SELECT DISTINCT ord2.ID as OrderId
FROM
(
SELECT ID, CustomerId, Status
FROM OrdersTable
WHERE Status = 0
ORDER BY created_at
LIMIT 1
) AS ord1
JOIN PurchasedProductsTable AS pprod1
ON pprod1.OrderId = ord1.ID
LEFT JOIN OrdersTable ord2
ON ord2.CustomerId = ord1.CustomerId
AND ord2.Status = ord1.Status
LEFT JOIN PurchasedProductsTable pprod2
ON pprod2.OrderId = ord2.ID
AND pprod2.itemSku = pprod1.itemSku
AND pprod2.Qty = pprod1.Qty
GROUP BY ord1.CustomerId, ord1.ID, ord2.ID
HAVING COUNT(pprod1.itemSku) = COUNT(pprod2.itemSku)
) q
JOIN OrdersTable AS o ON o.ID = q.OrderId;
Test on RexTester here
I have a table of products sales
id product_id price_sold
1 1 500
2 1 300
3 2 100
4 3 200
5 3 100
I want to be able to sum the prices by different subsets of products, say: sum of prices per the group of proucts 1,2. and another calculation of sum of prices per the group of products 2,3, so the needed result will be:
group 1, 900
group 2, 400
Can you help with efficient and elegant way to do that?
Doing what you want is a bit challenging, because the groups overlap. You have two options. The first is to do conditional aggregation and put the results in columns:
select sum(case when product_id in (1, 2) then price_sold end) as group1,
sum(case when product_id in (2, 3) then price_sold end) as group2
from productsales ps;
To get the results on separate rows, you could then pivot this result. Or, you could do the calculation directly. For this to work, you need to construct a table describing the groups:
select pg.grpid, sum(ps.price_sold)
from productsales ps
join
(
select 1 as grpid, 1 as product_id
union all
select 1 as grpid, 2 as product_id
union all
select 2 as grpid, 2 as product_id
union all
select 2 as grpid, 3 as product_id
) pg on ps.product_id = pg.product_id
group by pg.grpid;
SQL Fiddle:
SELECT 'GROUP 1' AS `Group`, SUM(price_sold) AS PriceSum
FROM MyTable
WHERE product_id = 1 OR product_id = 2
UNION
SELECT 'GROUP 2', SUM(price_sold)
FROM MyTable
WHERE product_id = 2 OR product_id = 3
The result looks like:
I tried asking question before, but it's hard to ask in specific without right terminology I am not quite familiar with. So here is an example
Take this query for example:
(
SELECT *
FROM comments
WHERE depth = 0
ORDER BY id DESC
LIMIT 2
)
UNION ALL
(
SELECT c.*
FROM comments c JOIN
(
SELECT id
FROM comments
WHERE depth = 0
ORDER BY id DESC
LIMIT 2
) p ON c.parent_id = p.id
LIMIT 5
)
id parent_id depth title
1 0 0 Title 1
2 0 0 Title 2
3 1 1 Title 3
4 1 1 Title 4
5 1 1 Title 5
6 1 1 Title 6
7 1 1 Title 7
I get two depth 0 rows and in join I get 5 child elements of those two returned queries as well. What I would like to get is to get 5 child elements of each of those two queries, total of 10 rows (of depth 1). For example:
id parent_id depth title
1 0 0 Title 1
2 0 0 Title 2
3 1 1 Title 3
4 1 1 Title 4
5 1 1 Title 5
6 1 1 Title 6
7 1 1 Title 7
8 2 1 Title 8
9 2 1 Title 9
10 2 1 Title 10
11 2 1 Title 11
12 2 1 Title 12
Is that even possible with adjacency list and a requirement to return everything as union (flat)?
edit:
Thanks to Bill Karwin's answer, I got it working now. I wonder still if there is a shorter way to write this. I have 6 (0-5) depth levels, so my query is rather long (and probably not optimal). Here is what it looks like for three levels (you can imagine what the full one looks like).
-- DEPTH LEVEL 0
(
SELECT * FROM (
SELECT *, 1 as _rn, #parent:=0
FROM comments
WHERE depth = 0
ORDER BY id DESC
LIMIT 2
) as D0
)
union all
-- DEPTH LEVEL 1
(
SELECT *
FROM (
SELECT c.*, #row:=IF(#parent=c.comment_id,#row+1,1) AS _rn, #parent:=c.comment_id
FROM (SELECT #parent:=null) AS _init
STRAIGHT_JOIN comments c
INNER JOIN
(
SELECT id
FROM comments
WHERE depth = 0
ORDER BY id DESC
LIMIT 2
) p ON c.comment_id = p.id
) AS _ranked
WHERE _ranked._rn <= 5
)
union all
-- DEPTH LEVEL 2
(
SELECT *
FROM (
SELECT c.*, #row:=IF(#parent=c.comment_id,#row+1,1) AS _rn, #parent:=c.comment_id
FROM (SELECT #parent:=null) AS _init
STRAIGHT_JOIN comments c
INNER JOIN
(
(
SELECT *
FROM (
SELECT c.*, #row:=IF(#parent=c.comment_id,#row+1,1) AS _rn, #parent:=c.comment_id
FROM (SELECT #parent:=null) AS _init
STRAIGHT_JOIN comments c
INNER JOIN
(
SELECT id
FROM comments
WHERE depth = 0
ORDER BY id DESC
LIMIT 2
) p ON c.comment_id = p.id
) AS _ranked
WHERE _ranked._rn <= 2
)
) p ON c.comment_id = p.id
) AS _ranked
WHERE _ranked._rn <= 2
)
You can't do this with LIMIT, because LIMIT is applied after the result set is completely finished, after all joining, grouping, sorting, etc.
You're using a variation of the greatest-n-per-group type of query. It's tricky to do this in MySQL because MySQL doesn't support the ROW_NUMBER() window function supported by many other SQL databases.
Here's a workaround for MySQL, in which user-defined variables can take the place of partitioned row numbers:
SELECT *
FROM (
SELECT c.*, #row:=IF(#parent=c.parent_id,#row+1,1) AS _rn, #parent:=c.parent_id
FROM (SELECT #parent:=null) AS _init
STRAIGHT_JOIN comments c
INNER JOIN
(
SELECT id
FROM comments
WHERE depth = 0
ORDER BY id DESC
LIMIT 2
) p ON c.parent_id = p.id
) AS _ranked
WHERE _ranked._rn <= 5
Say I have two tables I want to join.
Categories:
id name
----------
1 Cars
2 Games
3 Pencils
4 Books
And items:
id categoryid itemname
---------------------------
1 1 Ford
2 1 BMW
3 1 VW
4 2 Tetris
5 2 Pong
6 3 Foobar Pencil Factory
I want a query that returns the category and the last maximum N (for example: 2) itemname:
category.id category.name item.id item.itemname
-------------------------------------------------
1 Cars 2 BMW
1 Cars 3 VW
2 Games 4 Tetris
2 Games 5 Pong
3 Pencils 6 Foobar Pencil Factory
4 Books NULL NULL
I want write a query like below:
Select * From categories c
Left Join (select * from items order by id desc) i
On c.id=i=categoryid
AND LIMIT 2 #comment: N=2 this line not supported
Where i.categoryid = c.id
Group By c.id
Thanks!
I'm not saying it's efficient, but it should work:
SELECT c.*, i.id, i.itemname
FROM categories c
LEFT JOIN
(SELECT i.*
FROM items i
LEFT JOIN items i2 ON i.categoryid = i2.categoryid AND i2.id > i.id
GROUP BY i.id
HAVING COUNT(*) < 2 # this 2 = N
) i ON c.id = i.categoryid
Check http://sqlfiddle.com/#!2/9a132/1
SELECT *
FROM Categories c
LEFT JOIN -- Items i
(
SELECT * FROM Items WHERE LOCATE(id,
(
SELECT GROUP_CONCAT(it.itemids) AS its
FROM (
SELECT (SUBSTRING_INDEX(GROUP_CONCAT(CONVERT(id, CHAR(8))
ORDER BY id DESC), ',', 2)) AS itemids
FROM Items
GROUP BY categoryid
) it
)) <> 0
) i
ON i.categoryid = c.id;
where N=2 is: SUBSTRING_INDEX(GROUP_CONCAT(CONVERT(id, CHAR(8)) ORDER BY id DESC), ',', 2)
Because GROUP_CONCAT is by default sort ASC ; above will become SUBSTRING_INDEX(GROUP_CONCAT(CONVERT(id, CHAR(8)) ), ',', -2). But GROUP_CONCAT result is truncated to max len 1024 (group_concat_max_len).
I have 3 tables: items, purchases, and collaborators. A user can own an item, purchase an item, or be a collaborator on an item. Additionally, items that are purchased can be rated up, +1, or down, -1. An owner or collaborator can't purchase their own item.
I'd like to get all items for a given user and also display the ratings on each item.
Here's my tables:
items | purchases | collaborators
i_id item_id user_id | p_id item_id user_id rating |c_id item_id user_id
1 1 11 | 1 1 13 -1 | 1 1 12
2 2 12 | 2 2 11 1 | 2 2 13
3 3 13 | 3 3 12 NULL |
| 4 1 14 -1 |
Here's my MYSQL query so far:
select *, count(p_id) as tots, sum(rating=1) as yes, sum(rating= '-1') as no
from items
left join purchases
on items.item_id=purchases.item_id
left join collaborators
on items.item_id=collaborators.item_id
where items.user_id=13 or purchases.user_id=13 or collaborators.user_id=13
group by items.item_id
Here's my expected results for user_id=11 (changing each user_id in the WHERE clause):
item_id tots yes no
1 2 0 2
2 1 1 0
// notice how user_id=11 doesn't have anything to do with item_id=3
Here's my expected results for user_id=12:
item_id tots yes no
1 2 0 2
2 1 1 0
3 1 1 0
Here's my expected results for user_id=13:
item_id tots yes no
1 2 0 2
2 1 1 0
3 1 1 0
//notice user_id=13 should have same results as user_id=12. Although, their
relation to each of the 3 items is different, they still either purchased,
own, or collaboratored on each of them.
Unfortunately, I get the first two results but not the correct one for user_id=13.
For user_id=13, item_id=1 the tots=1 and not tots=2 for some reason I can't understand.
Any thoughts, such as, "its better to separate this into 2 queries", would be greatly appreciated,
I'm still not entirly sure I understand you correct but you could try following statement and let us work from there.
Edit
Following statement returns the expected results.
You can verify this (using SQL Server) here.
The gist of this is to
select all possible user_id and item_id combinations from your three tables
select the counts/ratings for each item
combine the results
SQL Statement
SELECT u.user_id, pt.item_id, pt.cnt, pt.yes, pt.no
FROM (
SELECT user_id, item_id, title FROM items
UNION SELECT user_id, item_id, NULL FROM purchases
UNION SELECT user_id, item_id, NULL FROM collaborators
) u INNER JOIN (
SELECT COUNT(*) AS cnt
, SUM(CASE WHEN ISNULL(rating, 1) = 1 THEN 1 ELSE 0 END) AS yes
, SUM(CASE WHEN rating =-1 THEN 1 ELSE 0 END) AS no
, item_id
FROM purchases
GROUP BY
item_id
) pt ON pt.item_id = u.item_id
MYSQL statement
SELECT u.user_id, pt.item_id, pt.cnt, pt.yes, pt.no, u.title
FROM (
SELECT user_id, item_id, title FROM items where user_id=13
UNION SELECT user_id, item_id, NULL FROM purchases where user_id=13
UNION SELECT user_id, item_id, NULL FROM collaborators where user_id=13
) u INNER JOIN (
SELECT COUNT(*) AS cnt
, SUM(rating=1) AS yes
, SUM(rating =-1) AS no
, item_id
FROM purchases
GROUP BY
item_id
) pt ON pt.item_id = u.item_id