I want to reduce the number of queries I'm making to my postgres database.
Currently I have this
select * from token_balances where asset_id = '36f813e4-403a-4246-a405-8efc0cbde76a' AND tick < yesterday ORDER BY tick DESC LIMIT 1;
select * from token_balances where asset_id = '36f813e4-403a-4246-a405-8efc0cbde76a' AND tick < last_week ORDER BY tick DESC LIMIT 1;
Is there some way I can make this into one query. Or is there even any need to reduce it?
Thanks
You can simply use the query with the greater date of tick. The first query already includes the results coming from the second one.
Just use the first query and you are good to go.
select * from token_balances where asset_id = '36f813e4-403a-4246-a405-8efc0cbde76a' AND tick < '2022-05-26T14:13:42.914Z' ORDER BY tick DESC LIMIT 1;
Rather than use yesterday (which is a valid reference) and last_week (which is not valid) just convert to date arithmetic. You can use simple date subtraction:
select *
from token_balances
where asset_id = '36f813e4-403a-4246-a405-8efc0cbde76a'
and tick < current_date - :num_days
order by tick desc
limit 1;
Related
with this query:
SELECT date_trunc('minute', ts) ts, instrument
FROM test
GROUP BY date_trunc('minute', ts), instrument
ORDER BY ts
I am grouping rows by minutes but I would like to generate a boolean value that tells me if, in the group, there is at least one row with the timestamp where the seconds are < 10 and at least one row with the timestamp where the seconds are > 50.
In short, something like:
lessThan10 = false
moreThan50 = false
for each row in the one minute group:
if row.ts.seconds < 10 then lessThan10 = true
if row.ts.seconds > 50 then moreThan50 = true
return lessThan10 && moreThan50
What I am trying to achieve is to find out if all the records I aggregate cover the beginning and the end of the minute; it's ok if there are holes here and there, but it's possible the data we capture stops and restarts at second 40 for example and, in that case, I'd like to be able to discard the whole minute.
As the data rate varies quite a lot, I can't check for a minimum number of row. There may be a better solution to achieve this, so I'm open to it as well.
Use EXTRACT() to get the seconds of the min and max values of ts:
SELECT date_trunc('minute', ts) ts, instrument,
EXTRACT(SECOND FROM MIN(ts)) < 10 lessThan10,
EXTRACT(SECOND FROM MAX(ts)) > 50 moreThan50
FROM test
GROUP BY date_trunc('minute', ts), instrument
ORDER BY ts
See the demo.
I have this sample database:
Table 1:
Type Condition_weight Price
A >50 1000
A >10 & <50 500
A <10 100
As I remember, I can do a comparison on the Condition_weight without doing too much on query.
My expectation query is something like this:
select Price from Table_1
where Type = 'A'
and {my_input_this_is a number} satisfy Condition_weight
I read it somewhere about this solution but cant find it again.
You can create a function that returns true - you will have to do the logic to extract min and max and compare value.
pseudo code...
CREATE FUNCTION conditionWeightIsSatisfed(number weight)
BEGIN
set #minValue = 0;
set #MaxValue = 1000;
..... do your conversion of the text values.....
select weight >= #minValue and weight <= #maxValue
END
I am trying to calculate the average of a column in Tableau, except the problem is I am trying to use a single date value (based on filter) from another data source to only calculate the average where the exam date is <= the filtered date value from the other source.
Note: Parameters will not work for me here, since new date values are being added constantly to the set.
I have tried many different approaches, but the simplest was trying to use a calculated field that pulls in the filtered exam date from the other data source.
It successfully can pull the filtered date, but the formula does not work as expected. 2 versions of the calculation are below:
IF DATE(ATTR([Exam Date])) <= DATE(ATTR([Averages (Tableau Test Scores)].[Updated])) THEN AVG([Raw Score]) END
IF DATEDIFF('day', DATE(ATTR([Exam Date])), DATE(ATTR([Averages (Tableau Test Scores)].[Updated]))) > 1 THEN AVG([Raw Score]) END
Basically, I am looking for the equivalent of this in SQL Server:
SELECT AVG([Raw Score]) WHERE ExamDate <= (Filtered Exam Date)
Below a workbook that shows an example of what I am trying to accomplish. Currently it returns all blanks, likely due to the many-to-one comparison I am trying to use in my calculation.
Any feedback is greatly appreciated!
Tableau Test Exam Workbook
I was able to solve this by using Custom SQL to join the tables together and calculate the average based on my conditions, to get the column results I wanted.
Would still be great to have this ability directly in Tableau, but whatever gets the job done.
Edit:
SELECT
[AcademicYear]
,[Discipline]
--Get the number of student takers
,COUNT([Id]) AS [Students (N)]
--Get the average of the Raw Score
,CAST(AVG(RawScore) AS DECIMAL(10,2)) AS [School Mean]
--Get the number of failures based on an "adjusted score" column
,COUNT([AdjustedScore] < 70 THEN 1 END) AS [School Failures]
--This is the column used as the cutoff point for including scores
,[Average_Update].[Updated]
FROM [dbo].[Average] [Average]
FULL OUTER JOIN [dbo].[Average_Update] [Average_Update] ON ([Average_Update].[Id] = [Average].UpdateDateId)
--The meat of joining data for accurate calculations
FULL OUTER JOIN (
SELECT DISTINCT S.[Id], S.[LastName], S.[FirstName], S.[ExamDate], S.[RawScoreStandard], S.[RawScorePercent], S.[AdjustedScore], S.[Subject], P.[Id] AS PeriodId
FROM [StudentScore] S
FULL OUTER JOIN
(
--Get only the 1st attempt
SELECT DISTINCT [NBOMEId], S2.[Subject], MIN([ExamDate]) AS ExamDate
FROM [StudentScore] S2
GROUP BY [NBOMEId],S2.[Subject]
) B
ON S.[NBOMEId] = B.[NBOMEId] AND S.[Subject] = B.[Subject] AND S.[ExamDate] = B.[ExamDate]
--Group in "Exam Periods" based on the list of periods w/ start & end dates in another table.
FULL OUTER JOIN [ExamPeriod] P
ON S.[ExamDate] = P.PeriodStart AND S.[ExamDate] <= P.PeriodEnd
WHERE S.[Subject] = B.[Subject]
GROUP BY P.[Id], S.[Subject], S.[ExamDate], S.[RawScoreStandard], S.[RawScorePercent], S.[AdjustedScore], S.[NBOMEId], S.[NBOMELastName], S.[NBOMEFirstName], S.[SecondYrTake]) [StudentScore]
ON
([StudentScore].PeriodId = [Average_Update].ExamPeriodId
AND [StudentScore].Subject = [Average].Subject
AND [StudentScore].[ExamDate] <= [Average_Update].[Updated])
--End meat
--Joins to pull in relevant data for normalized tables
FULL OUTER JOIN [dbo].[Student] [Student] ON ([StudentScore].[NBOMEId] = [Student].[NBOMEId])
INNER JOIN [dbo].[ExamPeriod] [ExamPeriod] ON ([Average_Update].ExamPeriodId = [ExamPeriod].[Id])
INNER JOIN [dbo].[AcademicYear] [AcademicYear] ON ([ExamPeriod].[AcademicYearId] = [AcademicYear].[Id])
--This will pull only the latest update entry for every academic year.
WHERE [Updated] IN (
SELECT DISTINCT MAX([Updated]) AS MaxDate
FROM [Average_Update]
GROUP BY[ExamPeriodId])
GROUP BY [AcademicYear].[AcademicYearText], [Average].[Subject], [Average_Update].[Updated],
ORDER BY [AcademicYear].[AcademicYearText], [Average_Update].[Updated], [Average].[Subject]
I couldn't download your file to test with your data, but try reversing the order of taking the average ie
average(IF DATE(ATTR([Exam Date])) <= DATE(ATTR([Averages (Tableau Test Scores)].[Updated]) then [Raw Score]) END)
as written, I believe you'll be averaging the data before returning it from the if statement, whereas you want to return the data, then average it.
is there a way to set an upper limit to a calculation (calculated field) which is already in a CASE clause? I'm calculating percentages and, obviously, don't want the highest value exceed '100'.
If it wasn't in a CASE clause already, I'd create something like 'case when calculation > 100.0 then 100 else calculation end as needed_percent' but I can't do it now..
Thanks for any suggestions.
I think using least function will be the best option.
select least((case when ...), 100) from ...
There is a way to set an upper limit on a calculated field by creating an outer query. Check out my example below. The inner query will be the query that you have currently. Then just create an outer query on it and use a WHERE clause to limit it to <= 1.
SELECT
z.id,
z.name,
z.percent
FROM(
SELECT
id,
name,
CASE WHEN id = 2 THEN sales/SUM(sales) ELSE NULL END AS percent
FROM
users_table
) AS z
WHERE z.percent <= 1
My table has a 'number' column which ranges from 0 to around 1000. I want to select everything from the table while ordering it by number. However, I want the rows with number=0 to appear last. I could do it in two queries:
select * from channel_table where number > 0 order by number;
select * from channel_table where number = 0;
But I'm guessing there is a one-line solution?
As you only have one exceptional case, you can use nullif with the nulls clause. Otherwise you would need to order by various case statements to get more complicated ordering logic.
select * from channel_table
order by nullif(number, 0) nulls last
Is this to simple?
select * from channel_table order by number desc;