If have the below query (simplified example of my query, for the purposes of readability):
SELECT make, year, color, count(*)
FROM cars
GROUPY BY make, year, color
ORDER BY 4 DESC;
I want to iterate through the resulting table and produce sub queries for the criteria of each row (examples below). I hope to then use these sub queries to make a single table with samples results (maybe 3 rows) that meet the criteria of each of the rows from the original query results (ex. as there are multiple Jeeps from 2019 in color black).
SELECT * from cars
WHERE make = 'Jeep'
AND year = '2019'
AND color = 'Black';
SELECT * from cars
WHERE make = 'Ford'
AND year = '2018'
AND color = 'Red';
This may seem like an odd or unnecessary request. However, I believe that this is the best approach given the complexity of my actual problem. This is the approach I want to take, as I want a simplified solution that I can come back to and alter for future use and for different variations of queries.
I am currently using ROW_NUMBER() to retrieve a maximum of three rows per group as my approach (below). Although this compiles for me, it has never run to completion because it has a very long runtime. When I go through the process manually (that I hope to automate with this query), the runtime to produce the desired output doesn't take too long (an hour or two). However, when I run this solution it remains running for the entire day and then Oracle stops the process as a result of the database connection timing out. Does anyone have a better approach to this problem, or perhaps a way to make this run more efficiently?
select *
from (
select c.*,
row_number() over(partition by make, year, color order by id) as rn
from cars c
) x
where rn <= 3
NOTE: I am using Oracle SQL Developer
You can get all queries by dynamically create another column like :
SELECT DISTINCT make, year, color,
'SELECT * from cars WHERE make =''' || make ||''' AND year = ''' || year ||''' AND color = ''' || color ||'''' AS SELECT_STATEMENTS
FROM (select *
from (
select c.*,
row_number() over(partition by make, year, color order by id) as rn
from cars c
) x
where rn <= 3)
Related
Please help me to optimize my SQL query.
I have a table with the fields: date, commodity_id, exp_month_id, exp_year, price, where the first 4 fields are the primary key. The months are designated with the alphabet-ordered letters: e.g. F (for Jan), G (for Feb.), H (for March), etc. Thus the letter of more distant from Jan. month will be larger than the letter of the less distant month (F < G < H < ...). Some commodity_ids have all 12 months in the table, some only 5 or 3, which are constant for all years.
I need to calculate the difference between prices (gradient) of the neighboring records in terms of exp_month_id, exp_year. As the first step, I want to define for every couple (exp_month_id, exp_year) the valid couple (next_month_id, next_year). The main problem here, that if the current exp_month_id is the last in the year, then next_year = exp_year + 1 and next_month_id should be the first one in the year.
I have written the following query to do the job:
WITH trading_months AS (
SELECT DISTINCT commodity_id,
exp_month_id
FROM futures
ORDER BY exp_month_id
)
SELECT DISTINCT f.commodity_id,
f.exp_month_id,
f.exp_year,
(
WITH [temp] AS (
SELECT exp_month_id
FROM trading_months
WHERE commodity_id = f.commodity_id
)
SELECT exp_month_id
FROM [temp]
WHERE exp_month_id > f.exp_month_id
UNION ALL
SELECT exp_month_id
FROM [temp]
LIMIT 1
)
AS next_month_id,
(
SELECT CASE WHEN EXISTS (
SELECT commodity_id,
exp_month_id
FROM trading_months
WHERE commodity_id = f.commodity_id AND
exp_month_id > f.exp_month_id
LIMIT 1
)
THEN f.exp_year ELSE f.exp_year + 1 END
)
AS next_year
FROM futures AS f
This query serves as a base for a dynamic table (view) which is subsequently used for calculating the gradient. However, the execution of this query takes more than one second and thus the whole process takes minutes. I wonder if you could help me optimizing the query.
Note: The following requires Sqlite 3.25 or newer for window function support:
Lack of sample data (Preferably as a CREATE TABLE and INSERT statements for easy importing) and expected results makes it hard to test, but if your end goal is computing the difference in prices between expiration dates (Making your question a bit of an XY problem, maybe something like:
SELECT date, commodity_id, price, exp_year, exp_month_id
, price - lag(price, 1) OVER (PARTITION BY commodity_id ORDER BY exp_year, exp_month_id) AS "change from last price"
FROM futures;
Thanks to the hint of #Shawn to use window functions I could rewrite the query in much shorter form:
CREATE VIEW "futures_nextmonths_win" AS
WITH trading_months AS (
SELECT DISTINCT commodity_id,
exp_month_id,
exp_year
FROM futures)
SELECT commodity_id,
exp_month_id,
exp_year,
lead(exp_month_id) OVER w AS next_month_id,
lead(exp_year) OVER w AS next_year
FROM trading_months
WINDOW w AS (PARTITION BY commodity_id ORDER BY exp_year, exp_month_id);
which is also slightly faster then the original one.
I need to match scrap records in one table with records indicating the material that was running at the same time on a machine. I have a table with the scrap counts and a table with records showing whenever the material changed on a machine.
I have a working query of which I will include a simplified version below, but it is very slow when applied to a large data set. I would like to try one of Oracle's analytical functions to make it faster, but I can't figure out how. I tried FIRST_VALUE, and ROW_NUMBER in a few different forms, but I couldn't get them right. Looking for any suggestions.
Please let me know if you would like more details.
Following are simplified versions of the tables:
Scrap readings table (~41m rows)
Machine
ScrapReasonCode
ScrapQuantity
ReportTime
Material numbers (~3m rows)
Machine
MaterialNumber
MEASUREMENT_TIMESTAMP
SELECT Scrap.Machine,
Scrap.MaterialNumber,
Scrap.ScrapReasonCode,
Scrap.ScrapQuantity,
Scrap.ReportTime
FROM Scrap, Materials
WHERE Scrap.Machine = Materials.Machine
AND Materials.MEASUREMENT_TIMESTAMP =
(SELECT MAX (M2.MEASUREMENT_TIMESTAMP)
FROM Materials M2
WHERE M2.Materials.Machine = Scrap.Machine
AND M2.MEASUREMENT_TIMESTAMP <= Scrap.ReportTime)
I think this is what you are trying to do. You can use the FIRST_VALUE window function.
SELECT DISTINCT
s.Machine,
s.MaterialNumber,
s.ScrapReasonCode,
s.ScrapQuantity,
s.ReportTime,
FIRST_VALUE(m.MEASUREMENT_TIMESTAMP) OVER(PARTITION BY s.Machine ORDER BY m.MEASUREMENT_TIMESTAMP DESC)
--or you can use the `MAX` window function too.
--MAX(m.MEASUREMENT_TIMESTAMP) OVER(PARTITION BY s.Machine)
FROM Scrap s
JOIN Materials m
WHERE s.Machine = m.Machine AND m.MEASUREMENT_TIMESTAMP <= s.ReportTime
I may be misunderstanding your requirements but I believe the following query should work in terms of implementing using ROW_NUMBER:
SELECT q.*
FROM (
SELECT ROW_NUMBER() OVER (PARTITION BY Scrap.Machine ORDER BY Materials.MEASUREMENT_TIMESTAMP DESC) AS RNO
Scrap.MaterialNumber,
Scrap.ScrapReasonCode,
Scrap.ScrapQuantity,
Scrap.ReportTime
FROM Scrap, Materials
WHERE Scrap.Machine = Materials.Machine
AND Materials.MEASUREMENT_TIMESTAMP <= Scrap.ReportTime
) q
WHERE q.RNO = 1
Edit: if you need the measurement timestamp before (rather than on-or-before) the Scrap ReportTime, you could just change the <= sign to a < sign in the query above.
I am trying to get the query below to return the TWO lowest PlayedTo results for each PlayerID.
select
x1.PlayerID, x1.RoundID, x1.PlayedTo
from P_7to8Calcs as x1
where
(
select count(*)
from P_7to8Calcs as x2
where x2.PlayerID = x1.PlayerID
and x2.PlayedTo <= x1.PlayedTo
) <3
order by PlayerID, PlayedTo, RoundID;
Unfortunately at the moment it doesn't return a result when there is a tie for one of the lowest scores. A copy of the dataset and code is here http://sqlfiddle.com/#!3/4a9fc/13.
PlayerID 47 has only one result returned as there are two different RoundID's that are tied for the second lowest PlayedTo. For what I am trying to calculate it doesn't matter which of these two it returns as I just need to know what the number is but for reporting I ideally need to know the one with the newest date.
One other slight problem with the query is the time it takes to run. It takes about 2 minutes in Access to run through the 83 records but it will need to run on about 1000 records when the database is fully up and running.
Any help will be much appreciated.
Resolve the tie by adding DatePlayed to your internal sorting (you wanted the one with the newest date anyway):
select
x1.PlayerID, x1.RoundID
, x1.PlayedTo
from P_7to8Calcs as x1
where
(
select count(*)
from P_7to8Calcs as x2
where x2.PlayerID = x1.PlayerID
and (x2.PlayedTo < x1.PlayedTo
or x2.PlayedTo = x1.PlayedTo
and x2.DatePlayed >= x1.DatePlayed
)
) <3
order by PlayerID, PlayedTo, RoundID;
For performance create an index supporting the join condition. Something like:
create index P_7to8Calcs__PlayerID_RoundID on P_7to8Calcs(PlayerId, PlayedTo);
Note: I used your SQLFiddle as I do not have Acess available here.
Edit: In case the index does not improve performance enough, you might want to try the following query using window functions (which avoids nested sub-query). It works in your SQLFiddle but I am not sure if this is supported by Access.
select x1.PlayerID, x1.RoundID, x1.PlayedTo
from (
select PlayerID, RoundID, PlayedTo
, RANK() OVER (PARTITION BY PlayerId ORDER BY PlayedTo, DatePlayed DESC) AS Rank
from P_7to8Calcs
) as x1
where x1.RANK < 3
order by PlayerID, PlayedTo, RoundID;
See OVER clause and Ranking Functions for documentation.
Suppose I have a database of athletic meeting results with a schema as follows
DATE,NAME,FINISH_POS
I wish to do a query to select all rows where an athlete has competed in at least three events without winning. For example with the following sample data
2013-06-22,Johnson,2
2013-06-21,Johnson,1
2013-06-20,Johnson,4
2013-06-19,Johnson,2
2013-06-18,Johnson,3
2013-06-17,Johnson,4
2013-06-16,Johnson,3
2013-06-15,Johnson,1
The following rows:
2013-06-20,Johnson,4
2013-06-19,Johnson,2
Would be matched. I have only managed to get started at the following stub:
select date,name FROM table WHERE ...;
I've been trying to wrap my head around the where clause but I can't even get a start
I think this can be even simpler / faster:
SELECT day, place, athlete
FROM (
SELECT *, min(place) OVER (PARTITION BY athlete
ORDER BY day
ROWS 3 PRECEDING) AS best
FROM t
) sub
WHERE best > 1
->SQLfiddle
Uses the aggregate function min() as window function to get the minimum place of the last three rows plus the current one.
The then trivial check for "no win" (best > 1) has to be done on the next query level since window functions are applied after the WHERE clause. So you need at least one CTE of sub-select for a condition on the result of a window function.
Details about window function calls in the manual here. In particular:
If frame_end is omitted it defaults to CURRENT ROW.
If place (finishing_pos) can be NULL, use this instead:
WHERE best IS DISTINCT FROM 1
min() ignores NULL values, but if all rows in the frame are NULL, the result is NULL.
Don't use type names and reserved words as identifiers, I substituted day for your date.
This assumes at most 1 competition per day, else you have to define how to deal with peers in the time line or use timestamp instead of date.
#Craig already mentioned the index to make this fast.
Here's an alternative formulation that does the work in two scans without subqueries:
SELECT
"date", athlete, place
FROM (
SELECT
"date",
place,
athlete,
1 <> ALL (array_agg(place) OVER w) AS include_row
FROM Table1
WINDOW w AS (PARTITION BY athlete ORDER BY "date" ASC ROWS BETWEEN 3 PRECEDING AND CURRENT ROW)
) AS history
WHERE include_row;
See: http://sqlfiddle.com/#!1/fa3a4/34
The logic here is pretty much a literal translation of the question. Get the last four placements - current and the previous 3 - and return any rows in which the athlete didn't finish first in any of them.
Because the window frame is the only place where the number of rows of history to consider is defined, you can parameterise this variant unlike my previous effort (obsolete, http://sqlfiddle.com/#!1/fa3a4/31), so it works for the last n for any n. It's also a lot more efficient than the last try.
I'd be really interested in the relative efficiency of this vs #Andomar's query when executed on a dataset of non-trivial size. They're pretty much exactly the same on this tiny dataset. An index on Table1(athlete, "date") would be required for this to perform optimally on a large data set.
; with CTE as
(
select row_number() over (partition by athlete order by date) rn
, *
from Table1
)
select *
from CTE cur
where not exists
(
select *
from CTE prev
where prev.place = 1
and prev.athlete = cur.athlete
and prev.rn between cur.rn - 3 and cur.rn
)
Live example at SQL Fiddle.
I am trying to wrap my head around this one this morning.
I am trying to show inventory status for parts (for our products) and this query only becomes complex if I try to return all parts.
Let me lay it out:
single table inventoryReport
I have a distinct list of X parts I wish to display, the result of which must be X # of rows (1 row per part showing latest inventory entry).
table is made up of dated entries of inventory changes (so I only need the LATEST date entry per part).
all data contained in this single table, so no joins necessary.
Currently for 1 single part, it is fairly simple and I can accomplish this by doing the following sql (to give you some idea):
SELECT TOP (1) ldDate, ptProdLine, inPart, inSite, inAbc, ptUm, inQtyOh + inQtyNonet AS in_qty_oh, inQtyAvail, inQtyNonet, ldCustConsignQty, inSuppConsignQty
FROM inventoryReport
WHERE (ldPart = 'ABC123')
ORDER BY ldDate DESC
that gets me my TOP 1 row, so simple per part, however I need to show all X (lets say 30 parts). So I need 30 rows, with that result. Of course the simple solution would be to loop X# of sql calls in my code (but it would be costly) and that would suffice, but for this purpose I would love to work this SQL some more to reduce the x# calls back to the db (if not needed) down to just 1 query.
From what I can see here I need to keep track of the latest date per item somehow while looking for my result set.
I would ultimately do a
WHERE ldPart in ('ABC123', 'BFD21', 'AA123', etc)
to limit the parts I need. Hopefully I made my question clear enough. Let me know if you have an idea. I cannot do a DISTINCT as the rows are not the same, the date needs to be the latest, and I need a maximum of X rows.
Thoughts? I'm stuck...
SELECT *
FROM (SELECT i.*,
ROW_NUMBER() OVER(PARTITION BY ldPart ORDER BY ldDate DESC) r
FROM inventoryReport i
WHERE ldPart in ('ABC123', 'BFD21', 'AA123', etc)
)
WHERE r = 1
EDIT: Be sure to test the performance of each solution. As pointed out in this question, the CTE method may outperform using ROW_NUMBER.
;with cteMaxDate as (
select ldPart, max(ldDate) as MaxDate
from inventoryReport
group by ldPart
)
SELECT md.MaxDate, ir.ptProdLine, ir.inPart, ir.inSite, ir.inAbc, ir.ptUm, ir.inQtyOh + ir.inQtyNonet AS in_qty_oh, ir.inQtyAvail, ir.inQtyNonet, ir.ldCustConsignQty, ir.inSuppConsignQty
FROM cteMaxDate md
INNER JOIN inventoryReport ir
on md.ldPart = ir.ldPart
and md.MaxDate = ir.ldDate
You need to join into a Sub-query:
SELECT i.ldPart, x.LastDate, i.inAbc
FROM inventoryReport i
INNER JOIN (Select ldPart, Max(ldDate) As LastDate FROM inventoryReport GROUP BY ldPart) x
on i.ldPart = x.ldPart and i.ldDate = x.LastDate