I created following syntax for two methods and cant put them together. Further I hope there's a shorter way to write this because it's not really lean:
#e = #c_entries.find_all{|i| i.order_no.between?(1,5)}
Gives me an array of all objects that's order_no is between 1 and 5!!
#f = #c_entries.all(:select => :order_no).collect(&:order_no).min
Creates an array of all order_no and gives me the minimum!
What I am trying now is to get the minimum order_no within all objects which order_no is between 1 and 5 as short as possible.
Any ideas?
If #c_entries contains a collection of particular model in your application, you can take advantage of ActiveRecord's query interface:
#c_entries.where(order_no: 1..5).select(:order_no).min
There are various other ways to narrow down your queries: http://guides.rubyonrails.org/active_record_querying.html#conditions
Related
I have two facts tables, First and Second, and two dimension tables, dimTime and dimColour.
Fact table First looks like this:
and facet table Second looks like this:
Both dim-tables have 1:* relationships to both fact tables and the filtering is one-directional (from dim to fact), like this:
dimColour[Color] 1 -> * First[Colour]
dimColour[Color] 1 -> * Second[Colour]
dimTime[Time] 1 -> * First[Time]
dimTime[Time] 1 -> * Second[Time_]
Adding the following measure, I would expect the FILTER-functuion not to have any affect on the calculation, since Second does not filter First, right?
Test_Alone =
CALCULATE (
SUM ( First[Amount] );
First[Alone] = "Y";
FILTER(
'Second';
'Second'[Colour]="Red"
)
)
So this should evaluate to 7, since only two rows in First have [Alone] = "Y" with values 1 and 6 and that there is no direct relationship between First and Second. However, this evaluates to 6. If I remove the FILTER-function argument in the calculate, it evaluates to 7.
There are thre additional measures in the pbix-file attached which show the same type of behaviour.
How is filtering one fact table which has no direct relationship to a second fact table affecting the calculation done on the second table?
Ziped Power BI-file: PowerBIFileDownload
Evaluating the table reference 'Second' produces a table that includes the columns in both the Second table, as well as those in all the (transitive) parents of the Second table.
In this case, this is a table with all of the columns in dimColour, dimTime, Second.
You can't see this if you just run:
evaluate 'Second'
as when 'evaluate' returns the results to the user, these "Parent Table" (or "Related") columns are not included.
Even so, these columns are certainly present.
When a table is converted to a row context, these related columns become available via RELATED.
See the following queries:
evaluate FILTER('Second', ISBLANK(RELATED(dimColour[Color])))
evaluate 'Second' order by RELATED(dimTime[Hour])
Similarly, when arguments to CALCULATE are used to update the filter context, these hidden "Related" columns are not ignored; hence, they can end up filtering First, in your example. You can see this, by using a function that strips the related columns, such as INTERSECT:
Test_ActuallyAlone = CALCULATE (
SUM ( First[Amount] ),
First[Alone] = "Y",
//This filter now does nothing, as none of the columns in Second
//have an impact on 'SUM ( First[Amount] )'; and the related columns
//are removed by the INTERSECT.
FILTER(
INTERSECT('Second', 'Second')
'Second'[Colour]="Red"
)
)
(See these resources that describe the "Expanded Table"
(this is an alternative but equivalent explanation of this behaviour)
https://www.sqlbi.com/articles/expanded-tables-in-dax/
https://www.sqlbi.com/articles/context-transition-and-expanded-tables/
)
I have a clickhouse table that has one Array(UInt16) column. I want to be able to filter results from this table to only get rows where the values in the array column are above a threshold value. I've been trying to achieve this using some of the array functions (arrayFilter and arrayExists) but I'm not familiar enough with the SQL/Clickhouse query syntax to get this working.
I've created the table using:
CREATE TABLE IF NOT EXISTS ArrayTest (
date Date,
sessionSecond UInt16,
distance Array(UInt16)
) Engine = MergeTree(date, (date, sessionSecond), 8192);
Where the distance values will be distances from a certain point at a certain amount of seconds (sessionSecond) after the date. I've added some sample values so the table looks like the following:
Now I want to get all rows which contain distances greater than 7. I found the array operators documentation here and tried the arrayExists function but it's not working how I'd expect. From the documentation, it says that this function "Returns 1 if there is at least one element in 'arr' for which 'func' returns something other than 0. Otherwise, it returns 0". But when I run the query below I get three zeros returned where I should get a 0 and two ones:
SELECT arrayExists(
val -> val > 7,
arrayEnumerate(distance))
FROM ArrayTest;
Eventually I want to perform this select and then join it with the table contents to only return rows that have an exists = 1 but I need this first step to work before that. Am I using the arrayExists wrong? What I found more confusing is that when I change the comparison value to 2 I get all 1s back. Can this kind of filtering be achieved using the array functions?
Thanks
You can use arrayExists in the WHERE clause.
SELECT *
FROM ArrayTest
WHERE arrayExists(x -> x > 7, distance) = 1;
Another way is to use ARRAY JOIN, if you need to know which values is greater than 7:
SELECT d, distance, sessionSecond
FROM ArrayTest
ARRAY JOIN distance as d
WHERE d > 7
I think the reason why you get 3 zeros is that arrayEnumerate enumerates over the array indexes not array values, and since none of your rows have more than 7 elements arrayEnumerates results in 0 for all the rows.
To make this work,
SELECT arrayExists(
val -> distance[val] > 7,
arrayEnumerate(distance))
FROM ArrayTest;
This is too tough for me guys. It's for Jeremy!
I have two tables (although I can also envision needing to join a third table) and I want to sum one field and count rows, in the same, table while joining with another table and return the result in json format.
First of all, the data type field that needs to be summed, is numeric(10,2) and the data is inserted as params['amount'].to_f.
The tables are expense_projects which has the name of the project and the company id and expense_items which has the company_id, item and amount (to mention just the critical columns) - the "company_id" columns are disambiguated.
So, the following code:
expense_items = DB[:expense_projects].left_join(:expense_items, :expense_project_id => :project_id).where(:project_company_id => company_id).to_a.to_json
works fine but when I add
expense_total = expense_items.sum(:amount).to_f.to_json
I get an error message which says
TypeError - no implicit conversion of Symbol into Integer:
so, the first question is why and how can this be fixed?
Then I want to join the two tables and get all the project names form the left (first table) and sum amount and count items in the second table. I have tried
DB[:expense_projects].left_join(:expense_items, :expense_items_company_id => expense_projects_company_id).count(:item).sum(:amount).to_json
and variations of this, all of which fails.
I would like a result which gets all the project names (even if there are no expense entries and returns something like:
project item_count item_amount
pr 1 7 34.87
pr 2 0 0
and so on. How can this be achieved with one query returning the result in json format?
Many thanks, guys.
Figured it out, I hope this helps somebody else:
DB[:expense_projects___p].where(:project_company_id=>user_company_id).
left_join(:expense_items___i, :expense_project_id=>:project_id).
select_group(:p__project_name).
select_more{count(:i__item_id)}.
select_more{sum(:i__amount)}.to_a.to_json
I need a little help with Linq i have a DB table with restourants tables in it. In the DB i have "TableNumber, Floor , RestaurantID" I would like to get list of all floors. For example if i have this list:
TableNumber, Floor , RestaurantID
10 1 1
11 1 1
12 2 1
13 2 1
14 3 1
I would like to get only "1,2,3".
Right now the method returns all rows.
public IEnumerable<ListPad.Item> GetFloorsListPads(SSF.ART.Key restaurant_id)
{
return from restaurant_floor in EnterpriseTouchRestaurantApplication.TouchRestaurant.AllRestaurantTables
where restaurant_floor.RestaurantID == restaurant_id && restaurant_floor.Active == true
orderby restaurant_floor.Floor
select new ListPad.Item()
{
Color = Color.SkyBlue,
Text = string.Format("{0}", restaurant_floor.Floor),
Tag = restaurant_floor
};
}
Thanks for all the help in advance.
You need either one or two things, depending of whether or not ListPad.Item defines equality (by overriding Equals and GetHashCode) in the way you describe. If so, then adding .Distinct() to your query will give you the distinct items. If not, you can do it one of three ways.
Return an anonymous type, call Distinct on it, and map to the actual type (lazy way)
Implement IEquatable on ListPad.Item, overriding Equals and GetHashCode (you'll need to research how to properly implement GetHashCode so it matches your equality conditions)
Define an IEqualityComparer<ListPad.Item> that defines your equality.
1 is the lazy way but is less coding. 2 is handy if your conditions define equality for ALL uses of ListPad.Item (not just this particular scenario). 3 separates the equality check from the actual type, which is handy if you have other cases where equality would be defined differently.
I have a set of rows which I've fetched from a table. Let's say the object Rating. After fetching this object, I have say 100 entries from the database.
The Rating object might look like this:
table_ratings
t.integer :num
So what I now want to do is perform some calculations on these 100 rows without performing any other queries. I can do this, running an additional query:
r = Rating.all
good = r.where('num = 2') # this runs an additional query
"#{good}/#{r.length}"
This is a very rough idea of what I want to do, and I have other more complex output to build. Let's imagine I have over 10 different calculations I need to perform on these rows, and so aliasing these in a sql query might not be the best idea.
What would be an efficient way to replace the r.where query above? Is there a Ruby method or a gem which would give me a similar query api into ActiveRecord Association collection objects?
Rating.all returns an array of all Rating objects. From there, shift your focus to selecting and mapping from the array. eg.:
#perfect_ratings = r.select{|x| x.a == 100}
See:
http://www.ruby-doc.org/core-1.9.3/Array.html
ADDITIONAL COMMENTS:
Going over the list of methods available for array, I find myself using the following frequently:
To check a variable against multiple values:
%w[dog cat llama].include? #pet_type # returns true if #pet_type == 'cat'
To create another array(map and collect are aliases):
%w[dog cat llama].map(|pet| pet.capitalize) # ["Dog", "Cat", "Llama"]
To sort and drop duplicates:
%w[dog cat llama dog].sort.uniq # ["cat", "dog", "llama"]
<< to add an element, + to add arrays, flatten to flatten embedded arrays into a single level array, count or length or size for number of elements, and join are the others I tend to use a lot.
Finally, here is an example of join:
%w[dog cat llama].join(' or ') # "dog or cat or llama"