In my app users can save sales reports for given dates. What I want to do now is to query the database and select only the latest sales reports (all those reports that have the maximum date in my table).
I know how to sort all reports by date and to select the one with the highest date - however I don't know how to retrieve multiple reports with the highest date.
How can I achieve that? I'm using Postgres.
Something like this?
SalesReport.where(date: SalesReport.maximum('date'))
EDIT: Just to bring visibility to #muistooshort's comment below, you can reduce the two queries to a single query (with a subselect), using the following form:
SalesReport.where(date: SalesReport.select('MAX(date)'))
If there is a lot of latency between your web host and your database host, this could halve execution times. It is almost always the preferred form.
You can get the maximum date to search for matching reports:
max_date = Report.maximum('date')
reports = Report.where(date: max_date)
Related
Good day to everyone! Hope all is well!
I am looking to run an update query or a group of queries that looks at my Date_Start and Date_End to determine if the Units (quantity of the respective record) fall in my defined current quarter 1/2/3/4 from another table (this table is a master table I’m using to provide the dates that I need to consider for defining the quarters).
I’ve been able to create queries that do this and then join them together to basically display the units out by quarter based on their respective start/end dates. The problem I am running into is this process takes a decent amount of time for the queries to populate that will drastically effect other processes down the line.
Thus we get to my desire. I am trying to no avail to create an update query that will update the quarter fields in my table based off of the queries I built to determine if the records start/end date fall in the respective quarter. I figure that running this update when records change will be an ok run time vs when I’m running reports or running an email script for the reports.
I have tried pulling in the table and query, joining them as equal on ID (the query pulls in the table's IDs), and selecting my field “CQ1” from the table, and setting the Update ether the respective field from the table or the query (which is the same as the field in the table).
All I get are the current values of the field in the data sheet view and an error of “Operation must use an updateable query.”
I have even tried placing a zero to see if that would do it with no luck. I have verified that all the fields are the same data type.
What am I doing wrong? Thanks!
Apologies to everyone.....I think my conscious brain was trying to overly complicate the process and while talking to a buddy about my issue distractedly created a new update query that worked. It all tied down to that I forgot to put a criteria on my quarter filed of is not null I believe. Thanks for anyone that has read this and is responding while I’m typing this or for those of you formulating a response.
I have two tables in PowerBI and a slicer, presented below in an abstracted way.
I want to know the number of orders placed for a customer in a given date range. This data is a sample for illustration - there are actually around 10,000 Customers and 500,000 Orders and both tables have many other fields, Ids etc.
My challenge -
Whilst this is easy enough do by relating the tables and doing a count, the difficulty comes in when I still want to see customers with 0 orders and on top of that I want this to work within a date range. In other words, instead of the customers with no orders disappearing form the list, I want them to appear in the list, but with a 0 value, depending on the date range. It would also be good if this could act as a measure, so I can see the number of total customers that have not ordered on a month by month basis. I have tried outer joins, merge queries, cross joins and lookups and cant seem to crack it.
Example 1: If I set the order date slicer to be: 02/01/2017 to 01/01/2018 I want the following results
Example 2: If I set the order date slicer to be: 03/01/2017 to 06/01/2017 I want the following results
Any help appreciated!
Thanks
This is entirely possible with a Measure. When you're using the Order field to count the rows for each customer, you're essential doing a COUNTROWS() function.
With your relationship still active, we can Prefix this in a measure to check for the blanks, and in those cases, return 0. something like this would work
Measure = IF(ISBLANK(COUNTROWS(Orders)),0,COUNTROWS(Orders))
In this case, 'Orders' is the table containing the Order and Order Date fields
My fact table contains details for clients who attend a course.
To ensure i can get a list of clients registered on any particular day, I have not related the date dimension to the fact table.
Instead i created a measure that does basic between logic (where startDate <= selectedDate && endDate >=SelectedDate)
This allows me to find all clients registered on one single selected day.
There are a few drawback to this however:
-I have to ensure the report user only selects a single day, i.e. they cannot select a date range.
-I cant easily do counts for samePeriodLastMonth or Year.
Is there a better design i should consider that will still allow me to see counts of registered clients on any given day, along with allowing me to use SamePeriodLastMonth/Year functionality?
Would you mind uploading the structure of your fact and dim tables?
Just a thought bubble: if you would like to measure counts for a program over calendar years, I believe you would definitely need to create a Date dimension. Also depending on your reporting needs you might want to consider whether you need an Accumulating Snapshot Fact table.
Please find further details on this:
http://www.kimballgroup.com/2012/05/design-tip-145-time-stamping-accumulating-snapshot-fact-tables/
Cheers
Nithin
Due to the PowerShell methods of getting mailbox statistics from Office365 taking about 2 seconds per mailbox, I am working on getting the data from Office 365 Reporting web service, which takes only a few seconds for each 2000 mailboxes.
The problem I'm running into is that the stats are updated periodically and some historical data is kept, so there are numerous records for each user. I only want to get the latest record for each user, but I haven't been able to find a way to do that. The closest I've come is to use $filter=Date ge DateTime'2016-03-10T00:00:00' where the date is concatenated to a couple of days ago. Theoretically, if I sort by Date desc I should get the latest records first, and if there is a user that has a record for 3/10 and 3/11, the 3/11 record would get pulled first, which would work for me. But regardless of how I do the sort it seems to come back with the older records first.
Ideally, I would like to be able to set criteria so that it only returns the latest record for each mailbox, but I can't seem to figure out or find how to do that. The closest I've been able to come is to just start running queries filtered on specific dates, walking the date back a day on each query.
If I can get the latest records to be returned first, I would be able to work with that because I can just discard a record if I've already received a later one.
https://reports.office365.com/ecp/reportingwebservice/reporting.svc/MailboxUsageDetail/
?DelegatedOrg=nnn.onmicrosoft.com&$select=Date,WindowsLiveID,CurrentMailboxSize
&$filter=Date ge DateTime'2016-03-08T00:00:00'&$orderby=Date desc
So the questions are:
Is there a way to specify criteria so that only the latest record for each user is returned?
Is there a way to get it to order by Date descending--what am I doing wrong with the $orderby?
Thanks!
You can use $top=1 to get latest record by applying $orderby on date (desc). $filter and $skip may not require in this case.
https://reports.office365.com/ecp/reportingwebservice/reporting.svc/MailboxUsageDetail/?DelegatedOrg=nnn.onmicrosoft.com&$select=Date,WindowsLiveID,CurrentMailboxSize&$orderby=Date desc&$top=1
Your query looks fine, here is an another example from Odata sample service to get employee detail with most recent birth date.
http://services.odata.org/V4/Northwind/Northwind.svc/Employees?$select=EmployeeID,FirstName,LastName,BirthDate&$orderby=BirthDate%20desc&$top=1
I'm looking to build an analytics dashboard for my data in a rails application.
Let's say I have a list of request types "Fizz", "Buzz", "Bang", "Bar".
I want to display a count for each day based on type.
How should I do this?
Here is what I plan on doing:
Add get_bazz_by_day, get_fizz_by_day, etc to the appropriate models.
In each model get all records of type Fizz, then create an array that stores date and count.
format in view so a JS library can format it into a pretty graph.
Does this sound reasonable?
Depending on number of records, your dashboard can soon get performance problems.
Step 1 is misleading. Don't get the data for each day individually, try to get them all at once.
In Step 2 you can have the database do the the aggregation over days, with the group method.
See http://guides.rubyonrails.org/active_record_querying.html#group
Fizz.select("date(created_at) as fizzed_day, count(*) as day_count").
group("date(created_at)")
In Step 3 you need to take care that days without any fizzbuzz are still displayed, as they are not returned in the query.