Data I have a table in Access that has a Part Number and PriceYr and Price associated to each Part Number.There are over 10,000 records and the PartNumber are repeated and has different PriceYr and Price associated to it. However, I need a query to just find the 5 most recent price and date associated with it.
I tried using MAX(PriceYr) however, it only returns 1 most recent record for each PartNumber.
I also tried the following query but it doesn't seem to work.
SELECT Catalogs.PartNumber,Catalogs.PriceYr, Catalogs.Price FROM Catalogs
WHERE Catalogs.PriceYr in
(SELECT TOP 5 Catalogs.PriceYr
FROM Catalogs as Temp
WHERE Temp.PartNumber = Catalogs.PartNumber
ORDER By Catalogs.PriceYr DESC)
Any help will be greatly appreciated. Thank you.
Desired Result that i am trying to get.
Consider a correlated count subquery to filter by a rank variable. Right now, you pull top 5 overall on matching PartNumber not per PartNumber.
SELECT main.*
FROM
(SELECT c.PartNumber, c.PriceYr, c.Price,
(SELECT Count(*)
FROM Catalogs AS Temp
WHERE Temp.PartNumber = c.PartNumber
AND Temp.PriceYr >= c.PriceYr) As rank
FROM Catalogs c
) As main
WHERE main.rank <= 5
MAX() is an aggregating function, meaning that it groups all the data and takes the maximal value in the specified column. You need to use a GROUP BY statement to prevent the query from grouping the whole dataset in a single row.
On the other hand, your query seems to needlessly use a subquery. The following query should work quite fine :
SELECT TOP 5 c.PartNumber, c.PriceYr, c.Price
FROM Catalogs c
ORDER BY c.PriceYr DESC
WHERE c.PartNumber = #partNumber -- if you want the query to
-- work on a specific part number
(please post a table creation query to make sure this example works)
Related
When I join to the right table I am getting way too many duplicates. I am trying to grab the most recent record from the right table however, it does not matter what I try it does not work.
So Far I have tried:
PROC SQL;
CREATE TABLE fs1.sample AS
SELECT A.*,
B.xx1,
max(B.time_s)
FROM lx1.results a left join (Select Distinct C.id, c.per FROM lx2.results c
Where c.id = a.id
and COMPGED(a.txt1, c.txt1,'i') < 100
and c.dt > a.dt
and c.ksv = 37
and datepart(c.lsg) >= '12DEC2020'd ) b
ON a.id = b.id
group by a.id, a.txt1
QUIT;
Unfortunately, I get an error. I also tried using case when exists, but that takes way too long. Essentially I am trying to grab the most recent record from the right table based on time_s. I also want to make sure the record I grab from the right table somewhat matches a.txt1.
Cheers
When you perform a join, you attach all records from the table that match your join conditions.
If the table is indexed appropriately, a subquery could achieve the goal of obtaining the most recent value, however, if the query uses the wrong index, TOP or equivalent functions may return the wrong result.
There are a number of ways to accomplish the task of retrieving the most recent record but they are contingent on a couple of things.
Firstly, you need to be able to identify what the most recent row is, usually by a column called CreatedDate or something similar against the IDs. (You should know what that business logic is, it may be that the table is chronologically entered [as most tables are] and therefore, SubID might be a thing. We're going to assume it is CreatedDate.)
Secondly, you need to rank the rows in terms of the CreatedDate in a descending order so that the newest matching ID is ranked 1.
Finally, you filter your results by 1 to return the newest result, but you could also filter by <= x if you are interested in the top x newest return results per ID.
To use more mathematical language: We are deriving a value from the CreatedDate and ID values and then using that derivative value to sort and filter the data. In this case we are deriving the RowNumber from the CreatedDate in descending order for each ID.
In order to accomplish this, you can use the Windowed Function ROW_NUMBER(),
ROW_NUMBER() OVER (PARTITION BY id ORDER BY CreatedDate DESC) as RankID
This windowed function will return a row value for each ID relative to the CreatedDate in descending order, where the newest created date is equal to 1.
You can then put brackets around the whole query to make it into a table so you will be able to filter the results of that Windowed Function.
SELECT id, txt
(SELECT id, txt
,ROW_NUMBER() OVER (PARTITION BY id ORDER BY CreatedDate DESC) as RankID
FROM SourceTable) A
WHERE RankID = 1
This should achieve your goal of returning the "newest result".
What ever your column is that determines the age of the data relative to the ID, it can be multiple, should be placed within the ORDER BY.
In order to make this query perform faster, you should index your data appropriately, whereby ID is the the first column, and CreatedDate Desc is your next column. This means your system will not have to perform a costly sort every time this runs, but that depends on whether you plan on using this query often and how much overhead it is grabbing.
I have read many answers here, but until now nothing could help me. I'm developing a ticket system, where each ticket has many updates.
I have about 2 tables: tb_ticket and tb_updates.
I created a SELECT with subqueries, where it took a long time (about 25 seconds) to get about 1000 rows. Now I changed it to INNER JOIN instead many SELECTs in subqueries, it is really fast (70 ms), but now I get duplicates tickets. I would like to know how can I do to get only the last row (ordering by time).
My current result is:
...
67355;69759;"COMPANY X";"2014-08-22 09:40:21";"OPEN";"John";1
67355;69771;"COMPANY X";"2014-08-26 10:40:21";"UPDATE";"John";1
The first column is the ticket ID, the second is the update ID... I would like to get only a row per ticket ID, but DISTINCT does not work in this case. Which row should be? Always the latest one, so in this case 2014-08-26 10:40:21.
UPDATE:
It is a postgresql database. I did not share my current query because it has only portuguese names, so I think it would not help at all.
SOLUTION:
Used_By_Already had the best solution to my problem.
Without the details of your tables one has to guess the field names, but it seems that tb_updates has many records for a single record in tb_ticket (a many to one relationship).
A generic solution to your problem - to get just the "latest" record - is to use a subquery on tb_updates (see alias mx below) and then join that back to tb_updates so that only the record that has the latest date is chosen.
SELECT
t.*
, u.*
FROM tb_ticket t
INNER JOIN tb_updates u
ON t.ticket_id = u.ticket_id
INNER JOIN (
SELECT
ticket_id
, MAX(updated_at) max_updated
FROM tb_updates
GROUP BY
ticket_id
) mx
ON u.ticket_id = mx.ticket_id
AND u.updated_at = mx.max_updated
;
If you have a dbms that supports ROW_NUMBER() then using that function can be a very effective alternative method, but you haven't informed us which dbms you are using.
by the way:
These rows ARE distinct:
67355;69759;"COMPANY X";"2014-08-22 09:40:21";"OPEN";"John";1
67355;69771;"COMPANY X";"2014-08-26 10:40:21";"UPDATE";"John";1
69759 is different to 69771, and that is enough for the 2 rows to be DISTINCT
there are difference in the 2 dates also.
distinct is a row operator which means is considers the entire row, not just the first column, when deciding which rows are unique.
Used_By_Already's solution would work just fine. I'm not sure on the performance but another solution would be to use cross apply, though that is limited to only a few DBMS's.
SELECT *
FROM tb_ticket ticket
CROSS APPLY (
SELECT top(1) *
FROM tb_updates details
ORDER BY updateTime desc
WHERE details.ticketID = ticket.ticketID
) updates
U Can try something like below if your updateid is identity column:
Select ticketed, max(updateid) from table
group by ticketed
To obtain last row you have to end your query with order by time desc then use TOP (1) in the select statement to select only the first row in the query result
ex:
select TOP (1) .....
from .....
where .....
order by time desc
We are in the process of optimizing our database.We have most of store procedure that uses CTE because it gives us high performance according to our table strucure.We have almost dynamic query that have different result according to different condition.We hold all data in CTE, and check condition, that was the not problem but we need total number of rows that return by each query ,in calculating this it takes lots of time.Temporary table or table variable not suitable in our case as it takes lots of time to insert data in it.We have structure as following
With t(fields) as
(select field1,field2.......
ROW_NUMBER() OVER (order by some column) as row...
from some table and lots of
inner n left joins
where some condition ),
rowTotal(RowTotal) as
(select max(row) from t)
select * from t,RowTotal
where condition for paging
But max(row) took lots of times if i remove this it return data within 100ms. I tried Coun(*),Count(SomeField) and many other it works but took lots of time.How can i achieve total number of rows from cte within some ms any aggregate function will not work for me.Is there any other way to calculate rowtotal like ##rowcount.Thanks in advance for any help.
If you are after the total number of rows from the inner query you can add this as a column to your select using COUNT() and PARTITION BY().
With t(fields) as
(select COUNT(*) OVER (PARTITION BY 1) AS TotalRows,
field1,field2.......
ROW_NUMBER() OVER (order by some column) as row...
from some table ...
This should give you a count of the total rows in 't' as the first column of t
I don't know that this is the fastest way to get the result you want but it works for me on 000's of returned records and prevents extra select queries to find the count separately.
I need to get the ID based from what ever the max amount is. Below is giving me an error
select ID from Prog
where Amount = MAX(Amount)
An aggregate may not appear in the WHERE clause unless it is in a subquery contained in a HAVING clause or a select list, and the column being aggregated is an outer reference.
The end result is that I need to get the just the ID as I need to pass it something else that is expecting it.
You need to order by Amount and select 1 record instead...
SELECT ID
FROM Prog
ORDER BY Amount DESC
LIMIT 1;
This takes all the rows in Prog, orders them in descending order by Amount (in other words, the first sorted row has the highest Amount), then limits the query to select only one row (the one with the highest Amount).
Also, subqueries are bad for performance. This code runs on a table with 200k records in half the time as the subquery versions.
Just pass a subquery with the max value to the where clause :
select ID from Prog
where Amount = (SELECT MAX(Amount) from Prog)
If you're using SQL Server that should do it :
SELECT TOP 1 ID
FROM Prog
ORDER BY Amount DESC
This should be something like:
select P.ID from Prog P
where P.Amount = (select max(Amount) from Prog)
EDIT:
If you really want only 1 row, you should do:
select max(P.ID) from Prog P
where P.Amount = (select max(Amount) from Prog);
However, if you have multiple rows that would match amount and you only want 1 row, you should have some kind of logic behind how you pick your one row. Not just relying on this max trick, or limit 1 type logic.
Also, I don't write limit 1, because this is not ANSI sql -- it works in mysql but OP doesn't say what he wants. Every db is different -- see here: Is there an ANSI SQL alternative to the MYSQL LIMIT keyword? Don't get used to one db's extensions unless you only want to work in 1 db for the rest of your life.
select min(ID) from Prog
where Amount in
(
select max(amount)
from prog
)
The min statement ensures that you get only one result.
I have a very large query that is supposed to return only the top 10 results:
select top 10 ProductId from .....
The problem is that I also want the total number of results that match the criteria without that 'top 10', but in the same time it's considered unaceptable to return all rows (we are talking of roughly 100 thousand results.
Is there a way to get the total number of rows affected by the previous query, either in it or afterwords without running it again?
PS: please no temp tables of 100 000 rows :))
dump the count in a variable and return that
declare #count int
select #count = count(*) from ..... --same where clause as your query
--now you add that to your query..of course it will be the same for every row..
select top 10 ProductId, #count as TotalCount from .....
Assuming that you're using an ORDER BY clause already (to properly define which the "TOP 10" results are), then you could add a call of ROW_NUMBER also, with the opposite sort order, and pick the highest value returned.
E.g., the following:
select top 10 *,ROW_NUMBER() OVER (order by id desc) from sysobjects order by ID
Has a final column with values 2001, 2000, 1999, etc, descending. And the following:
select COUNT(*) from sysobjects
Confirms that there are 2001 rows in sysobjects.
I suppose you could hack it with a union select
select top 10 ... from ... where ...
union
select count(*) from ... where ...
For you to get away with this type of hack you will need to add fake columns to the count query so it returns the same amount of columns as the main query. For example:
select top 10 id, first_name from people
union
select count(*), '' as first_name from people
I don't recommend using this solution. Using two separate queries is how it should be done
Generally speaking no - reasoning is as follows:
If(!) the query planner can make use of TOP 10 to return only 10 rows then RDBMS will not even know the exact number of rows that satisfy the full criteria, it just gets the TOP 10.
Therefore, when you want to find out count of all rows satisfying the criteria you are not running it the second time, but the first time.
Having said that proper indexes might make both queries execute pretty fast.
Edit
MySQL has SQL_CALC_FOUND_ROWS which returns the number of rows that query would return if there was no LIMIT applied - googling for an equivalent in MS SQL points to analytical SQL and CTE variant, see this forum (even though not sure that either would qualify as running it only once, but feel free to check - and let us know).