This is about relational algebra,
I have a table and im always having the problem of not being able to project what I want, but I think im almost right. For example, in this case I need to find all the pizzerias that female customers attend,
this is my algorithm
πname Frequents ⨝(πname σgender='female' Person) ,
in this case, I found all the names of each customer, and on the Frequents Table I want to display the pizzerias. How would I be able to do so?
I thought about doing
πpizzeria (πname Frequents ⨝(πname σgender='female' Person) Frequents or
πpizzeria σname = (πname Frequents ⨝(πname σgender='female' Person) Frequents
but it gives me an error.
The tables are on the photo.
Thank you in advance!
the whole group is on this pasteit file here
Related
I don't know if I even worded the question correctly, but I'm trying to create a measure that depends on what is showing in the pivot table (using PowerPivot). In the image I posted, "DealMonth" is an expression in the PowerQuery table itself that simply takes the start date of the employee and subtracts it from the month a deal was closed in. That will show how long it took for that salesperson to close the deal. "TenureMonths" is also an expression in the PowerQuery table that calculates the tenure of the person. The values populating this screenshot are coming from a total headcount measure created. What I'm trying to do is create a separate measure that will show when the "TenureMonths" is less than the "DealMonth." So if the TenureMonths is 5, then after DealMonth of 5, the value would be 0. Is this possible?
Screenshot
I should add the following information.
"DealMonth" - Comes from the FactData table
"TenureMonths" - Comes from the DimSalesStart table
These two tables are joined by name. I feel like I'm so close because I can see what I want. The second image below is a copy/paste of the pivot table result but with my edits to show what I'd want to have shown. Basically, if(TenureMonths >= DealMonth,1,0). The trouble seems to be that since they're in two different tables, I can't make it work. The rows in the fact table are transactions, but the rows in the dim table are just the people with their start and end dates.
Desired Result
This is possible with some IF([measure1]<[measure2],blank(),[measure1]), however without seeing more of the data it will be hard to guide you specifically.
However you need to create two separate measures, one for TenureMonths and one for DealMonth, depending on the data this can be done with an aggregator forumla such as sum, min, max, etc (depends if there will be more than one value).
Then reference those two measures in the formula pattern I mentioned above, and that should give you want you want.
I figured out a solution. I added a dimension table for DealMonth itself and joined to my fact table. That allowed me to do the formulas that I needed.
I've looked at many threads regarding COUNT and COUNTA, but I can't seem to figure out how to use it correctly.
I am new to DAX and am learning my way around. I have attempted to look this up and have gotten a little ways to where I need to be but not exactly. I think I am confused about how to apply a filter.
Here's the situation:
Four separate queries used to generate the data in the report; but only need to use two for the DAX function (Products and Display).
I have three columns I need to filter by, as follows:
Customer (Display or Products query; can do either)
Brand (Products query)
Location (Display query)
I want to count the columns based on if the data is unique.
Here's an example:
Customer: Big Box Buy;
Item: Lego Big Blocks;
Brand: Lego;
Location: Toys;
BREAK
Customer: Big Box Buy;
Item: Lego Star Wars;
Brand: Lego;
Location: Toys;
BREAK
Customer: Big Box Buy;
Item: Surface Pro;
Brand: Microsoft;
Location: Electronics;
BREAK
Customer: Little Shop on the Corner;
Item: Red Bicycle;
Brand: Trek;
Location: Racks;
In this example, no matter the fact that the items are different, we want to look at just the customer, the brand, and the location. We see in the first two records, the customer is "Big Box Buy" and the brand is "Lego" and the location is "Toys". This appears twice, but I want to count it distinct as "1". The next "Big Box Buy" store has the brand "Microsoft" and the location is "Electronics". It appears once and only once, and thus the distinct count is "1" anyway. This means that there are two separate entries for "Big Box Buy", both with a count of 1. And lastly there is "Little Shop on the Corner" which appears just once and is counted just once.
The "skeleton" of the code I have is basically just to see if I can get a count to work at all, which I can. It's the FILTER that I think is the problem (not used in the below example) judging by other threads I've read.
TotalDisplays = CALCULATE(COUNTA(products[Brand]))
Obviously I can't just count the amount of times a brand appears as that would give me duplicates. I need it unique based on if the following conditions are met:
Customer must be the same
Brand must be the same
Location must be the same
If so, we distinctly count it as one.
I know I ranted a bit and may seem to have gone in circles, but I was trying to figure out how to explain it. Please let me know if I need to edit this post or post clarification.
Many thanks in advance as I go through my journey with DAX!
I believe I have the answer. I used a NATURALINNERJOIN in DAX to create a new, merged table since I needed to reference all values in the same query (couldn't figure out how to do it otherwise). I also created an "unique identity" calculated column that combined data from multiple rows, but was hidden behind the scenes (not actually displayed on the report) so I could then take a measure of the unique values that way.
TotalDisplays = COUNTROWS(DISTINCT('GD-DP-Merge'[DisplayCountCalcCol]))
My calculated column is as follows:
DisplayCountCalcCol = 'GD-DP-Merge'[CustID] & 'GD-DP-Merge'[Brand] & 'GD-DP-Merge'[Location] & 'GD-DP-Merge'[Order#]
So the measure TotalDisplays now reports back the distinct count of rows based on the unique value of the customer ID, the brand, and the location of the item. I also threw in an order number just in case.
Thanks!
I am semi new to DAX and was struggling with Count and CountA formula, you post has helped me with answers. I would like to add the solution which i got for my query: Wanted count for Right Time start Achieved hence if anyone is looking for this kind of answer use below, filter will be selecting the table and adding string which you want to
RTSA:=calculate(COUNTA([RTS]),VEO_Daily_Services[RTS]="RTSA")
I've got 2 classes
Reports - objectID, Title, Date & relationItem ( Relation type column linked up to Items)
Items - ObjectID, Title, Date etc
I want to query all the Items that are equal to a objectID in reports. Users create reports then add items to them. These items are found in the Items table.
I've looked at the https://parseplatform.github.io/docs/ios/guide/#relations but don't see anything for swift3.
I've tried a few things with little success. This snipplet below i did find, but not sure how to apply it to my classes.
var relation = currentUser.relationForKey("product")
relation.query()?.findObjectsInBackgroundWithBlock({
Would love somebody to direct me into the right direction! Thanks
Tried this code below too!
var query = PFQuery(className:"Items")
query.whereKey("relationItem ", equalTo: PFObject(withoutDataWithClassName:"Reports", objectId:"MZmMHtobwQ"))
Ok so i had to change the table slightly to get this to work to prevent a query within a query.
I've added a relation Type to the Items table instead of the Reports Table
Then i managed to retrieve all the Items based of that report ObjectId like this:
let query = PFQuery(className:"Items")
query.whereKey("reportRelation", equalTo: PFObject(withoutDataWithClassName:"Reports", objectId:"3lWMYwWNEj"))
This then worked. Note that reportRelation is the Relational Type Column.
Thanks
When you’re thinking about one-to-many relationships and whether to implement Pointers or Arrays, there are several factors to consider. First, how many objects are involved in this relationship? If the “many” side of the relationship could contain a very large number (greater than 100 or so) of objects, then you have to use Pointers. If the number of objects is small (fewer than 100 or so), then Arrays may be more convenient, especially if you typically need to get all of the related objects (the “many” in the “one-to-many relationship”) at the same time as the parent object.
http://parseplatform.github.io/docs/ios/guide/#relations
If you are working with one to many relation, use pointer or array. See the guide for examples and more explanation.
I am new to Qlik and trying to solve the following issue.
I have a table with two dimensions, one with the entry's unique ID, and one with a category, as in the example below.
Table example
My goal is to create a new column with a ranking of 'Score' - my measure - per category:
Table with desired output
If I use the expression
Rank(Score)
I get a column of ones, as the command takes the most granular dimension (Unique ID) as the default one. If I use
Rank(TOTAL Score)
It obviously returns a ranking regardless of all the dimensions. By reading the documentation and similar questions asked by other users I reckon that it should be possible to specify which dimension to use for TOTAL, with the following syntax:
Rank(TOTAL <Category> Score)
Yet, the formula returns an error and only null column values. I've tried different syntax, use of brackets but I still cannot grasp what I am doing wrong.
Please note that I cannot create the ranking column when loading the data.
I would immensely appreciate if someone were so kind to help on this!
Try with
=aggr(rank(sum(Score)), Category, UniqueID)
I have a dataset which has files of hotel reviews. Each file contains multiple reviews for a single hotel. Here are my two relations in BCNF:
Hotel(hotelID, OverallRating, AveragePrice, URL)
Review(hotelID, Author, Content, Date, No. Reader, No. Helpful,
Overall, Value, Rooms, Location, Cleanliness, Checkin / front desk,
Service, Business Service)
I am trying to write the following query in relational algebra:
Find all the reviews by the same user (i.e., given a user ID, return the list of all their
reviews).
By User ID, the question is referring to the Author attribute found in my second relation. The way I understand the question, it must take a user ID as an argument. Maybe you see it differently?
Here is what I have so far:
(Selection) Author = $1 (Review)
Replace selection with the sigma symbol used to represent selection in relational algebra, I was having trouble inserting it into my question. $1 represents where it would take the user ID argument, this is just to show my thinking, I do not think its correct.
Thanks for your time
Query will be:
σ(Author="Your_User Id") ( Hotel Join(X)(Hotel.hotelID=Review.hotelID) Review )
Where
σ = Selection Operator
X= Join Operator
(-----) = Condition
Hope it helps. For More detail Refer My notes for DBMS: Relational Algebra
Search "Relational Algebra" Term in site to find your exact information fast.