I'm implementing a search functionality where the results should show results page and for each result, the main image and up to 3 more thumbnails.
Right now in the procution version, for each ad it makes 1 select to return the images from the database which it terrible for performance, so I've changed it to a single query that does basically the following:
select * from AdImages order by IsMainImage desc, AdImageId
and returns something like:
AdImageId AdId IsMainImage FilePath
----------- ----------- ----------- ----------------------------------------
1 1 1 9c513f10-5480-4e41-89c6-074b36051999.jpg
5 2 1 f64f9c12-398e-445f-9724-baebe40930b1.jpg
6 4 1 8187d566-b296-4ab0-85e5-b9fc86f293b7.jpg
8 5 1 b8165008-09b3-4258-bf54-043195138344.jpg
10 6 1 86c636ed-f4ed-4f7e-8c7e-fc0b24faa956.jpg
11 7 1 4409a3fd-2bc0-4512-9850-6f5146193e50.jpg
13 8 1 b9b66c48-92b7-479a-a85d-dc6d26b03ebc.jpg
14 9 1 9f3f06ad-4fe1-43a5-8cce-3bb804bb10b7.jpg
16 10 1 016c30dc-5ee8-40d8-9d0f-398f444d7a7b.jpg
19 11 1 e5e56602-1af7-492b-8a8e-b61ac86b751b.jpg
2 1 0 02d44ce1-0de6-4e22-b4ef-043a72e9b5e8.jpg
3 1 0 8c4e19db-faff-44c2-9aab-6a96ab2a8e22.jpg
4 1 0 d8c2464a-277c-40fa-ab43-d2455e819e7e.jpg
7 4 0 d1430ae0-df51-43b7-acea-50d606eee5ba.jpg
9 5 0 b947ae4c-653d-4c27-9edd-567d977e1af3.jpg
12 7 0 3080c947-3769-4762-bb29-f1f9c5303ecd.jpg
15 9 0 d2543ce3-1e65-4a18-80d6-584de0025f1a.jpg
17 10 0 03b26d6a-4e0c-4393-9b5a-d9f2a24d36da.jpg
18 10 0 cde5dacd-3984-4cea-b56f-c3a6c5b82fa0.jpg
20 11 0 9e286ac0-25b1-4a05-af83-26e5d0002c2a.jpg
21 11 0 b1266770-9926-462c-8ec0-e965b21021eb.jpg
22 11 0 0542bd2a-4c4b-41d4-b51b-d311f42f0da9.jpg
23 11 0 b1cc44c9-50c4-4e81-bc9a-a0a4b515e709.jpg
My local db is very small but I could notice a very good performance gain, anyway, I think it could be better if I could make this query return only up to 4 rows for each ad instead of all the rows for each ad as it is doing. But to do so, it should be something like where count(AdId) == 4 which I'm not sure is possible.
I'm also using Entity Framework here. Any extra advice would be very welcome.
Use Window Function
select AdImageId ,AdId ,IsMainImage ,FilePath
from(
select row_number() over(partition by Adid order by IsMainImage desc, AdImageId) rn,*
from AdImages)a
where rn<=4
If I am understanding you correctly, you can just return the TOP xx results.
SELECT TOP(3) * from AdImages order by IsMainImage desc, AdImageId;
This will return only the top 3 results.
Related
Please see the following pic and i want to convert this formula in SQL Server.
in excel sheet
M N
15 1 0
16 3 1
17 5 2
18 8 4
19 9 4
N= IF(M16-M15<=1,N15,M16-M15-1+N15
Please see the screenshot for reference:
As per your tags, this can be done with LAG and then doing a running total.
For each row, first calculate the difference in M from the previous row (using LAG) - I call this Dif_Last_M. This mirrors the 'M24-M23' part of your formula.
If Dif_Last_M is <= 1, add 0 to the running total (effectively making the running total the same as for the previous row)
Else if Dif_Last_M is > 1, add (Dif_Last_M minus 1) to the running total
Here is the code assuming your source table is called #Temp and has an ID (sorting value)
WITH M_info AS
(SELECT ID, M, (M - LAG(M, 1) OVER (ORDER BY ID)) AS Dif_Last_M
FROM #Temp
)
SELECT ID,
M,
SUM(CASE WHEN Dif_Last_M > 1 THEN Dif_Last_M - 1 ELSE 0 END) OVER (ORDER BY ID) AS N
FROM M_info;
And here are the results
ID M N
1 1 0
2 3 1
3 5 2
4 8 4
5 9 4
6 12 6
7 13 6
Here is a db<>fiddle with the above. It also includes additional queries showing
The result from the CTE
The values used in the running total
Note that while it possible to do this with recursive CTEs, they tend to have performance problems (they are loops, fundamentally). Soit is better (performance-wise) to avoid recursive CTEs if possible.
Consider the following tables
group (obj_id here is user_id)
group_id obj_id role
--------------------------
100 1 A
100 2 root
100 3 B
100 4 C
notes
obj_id ref_obj_id note note_id
-------------------------------------------
1 2 10
1 3 10
1 0 foobar 10
1 4 20
1 2 20
1 0 barbaz 20
2 0 caszes 30
2 1 30
4 1 70
4 0 taz 70
4 3 70
Note: a note in the system can be assigned to multiple users (for instance: an admin could write "sent warning to 2 users" and link it to 2 user_ids). The first user the note gets linked to is stored differently than the other linked users. The note itself is linked to the first linked user only. Whenever group.obj_id = notes.obj_id then ref_obj_id = 0 and note <> null
I need to make an overview of the notes per user. Normally I would do this by joining on group.obj_id = notes.obj_idbut here this goes wrong because of ref_obj_id being 0 (in which case I should join on notes.obj_id)
There are 4 notes in this system (foobar, barbaz, caszes and taz).
The desired output is:
obj_id user_is_primary notes_primary user_is_linked notes_linked
-------------------------------------------------------------------
1 2 10;20 2 30;70
2 1 30 2 10;20
3 0 2 10;70
4 1 70 1 20
How can I get to this aggregated result?
I hope that I was able to explain the situation clearly; perhaps it is my inexperience but I find the data model not the most straightforward.
Couldn't you simply put this in the ON clause of your join?
case when notes.ref_obj_id = 0 then notes.obj_id else notes.ref_obj_id end = group.obj_id
I've looked for an example question like this, I ask for grace if it's been answered (I thought it would have been but have a hard time finding meaningful results with the terms I searched.)
I work at a manufacturing plant where at ever manufacturing operation a part is issued a new serial number. The database table I have to work with has the serial number recorded in the Container field and the previous serial number the part had recorded in the From_Container field.
I'm trying to SUM the Extended_Cost column on parts we've had to re-do operations on.
Here's a sample of data from tbl_Container:
Container From_Container Extended_Cost Part_Key Operation
10 9 10 PN_100 60
9 8 10 PN_100 50
8 7 10 PN_100 40
7 6 10 PN_100 30
6 5 10 PN_100 20
5 4 10 PN_100 50
4 3 10 PN_100 40
3 2 10 PN_100 30
2 1 10 PN_100 20
1 100 10 PN_100 10
In this example the SUM I would expect returned is 40, because operations 20, 30, 40 and 50 were all re-done and cost $10 each.
So far I've been able to do this by rejoining the table to itself 10 times using aliases in the following fashion:
LEFT OUTER JOIN tbl_Container AS FCP_1
ON tbl_Container.From_Container = FCP_1.Container
AND FCP_1.Operation <= tbl_Container.Operation
AND tbl_Container.Part_Key = FCP_1.Part_Key
And then using SUM to add the Extended_Cost fields together. However, I'm violating the DRY principle and there has got to be a better way.
Thank you in advance for your help,
Me
You can try this query.
;WITH CTE AS
(
SELECT TOP 1 *, I = 0 FROM tbl_Container C ORDER BY Container
UNION ALL
SELECT T.*, I = I + 1 FROM CTE
INNER JOIN tbl_Container T
ON CTE.Container = T.From_Container
AND CTE.Part_Key = T.Part_Key
)
SELECT Part_Key, SUM(T1.Extended_Cost) Sum_Extended_Cost FROM CTE T1
WHERE
EXISTS( SELECT * FROM
CTE T2 WHERE
T1.Operation = T2.Operation
AND T1.I > T2.I )
GROUP BY Part_Key
Result:
Part_Key Sum_Extended_Cost
---------- -----------------
PN_100 40
I have the following scenario:
Table is _etblpricelistprices
Columns are as follows:
iPriceListNameID iPricelistNameID iStockID fExclPrice
1 1 1 10
2 2 1 20
3 3 1 30
4 4 1 40
5 5 1 100
6 6 1 200
7 7 1 300
8 8 1 400
9 1 2 1000
10 2 2 2000
11 3 2 3000
12 4 2 4000
13 5 2 50
14 6 2 40
15 7 2 30
16 8 2 20
There are only two stock items here, but a lot more in the DB. The first column is the PK which auto-increments. The second column is the Pricelist. The pricelist is split as follows. (1-4) is current pricing and (5-8) is future pricing. the third column is the stock item's ID, and the fourth column, the pricing of the item.
I need a script to update this table to swap the future and current pricing per item. Please help
Observe, if you will, that swapping the iPricelistNameID values will achieve the same overall effect as swapping the fExclPrice values, and can be perfomed using a formula:
UPDATE _etblpricelistprices
SET
iPricelistNameID = CASE
WHEN iPricelistNameID > 4 THEN iPricelistNameID - 4
ELSE iPricelistNameID + 4
END
for a table on ms-sql2000 containing the following columns and numbers:
S_idJ_id Se_id B_id Status Count multiply
63 1000 16 12 1 10 2
64 1001 12 16 1 9 3
65 1002 17 12 1 10 2
66 1003 16 12 1 6 3
67 1004 12 16 1 10 2
I want to generate an classic asp script which will do the following for each row
where status=1 :
-multiply -> answer= multiply column 'count' with column 'multiply'
Then:
count the total answer and sum for each se_id like :
se_id total
12 47
16 38
17 20
and display on screen like
Rank se_id total
1 12 47
2 16 38
3 17 20
Condition:
if there are multiple equal total values then give the lower numbered se_id a priority for
getting a ranking and give the next higher numbered se_id the next number in rank
Any sample code in classic asp or advice is welcome on how to get this accomplished
'score' = source table.
if (EXISTS (select * from INFORMATION_SCHEMA.TABLES where TABLE_NAME = 'result_table'))
begin
drop table result_table;
end
select
rank = IDENTITY(INT,1,1),
se_id, sum(multiply * count) as total
into result_table
from score
where status = 1
group by se_id
order by total desc, se_id;
[Edit] Change query as answer on first comment