Extracting multiple values from the same column, X, given their shared value in column Y - sql

Before everything, I would like to say thanks for your help! I am currently working on data provided by UK rail; the data I have is currently contained in a relational database on PostgreSQL. My ultimate goal is to extract origin-destination pairs that are served by the railway network.
Right now, entries are stored in rows that each contain one stop/location in a train's journey. For instance, if a train travels from D to G via E and F, then D will be contained in a row and marked as an origin_location, E and F as an intermediate_location and G as a terminating_location. Each of them will also be marked with additional details such as train ID, time of the departure/passage/arrival and date of travel.
Eventually, from these entries I hope to write a query that gives me all possible origin-destination pairs. So for instance, continuing the example above, I would like the query to produce a table that gives me rows as such: D-E; D-F; D-G; E-F; E-G; F-G. The linkages between these locations are based on them sharing a common train identifier that is in another column, "Column Y".
I am at the very start of my research, but I don't expect you to help me find a specific code as a solution. Rather, I just hope you could point me in the direction as to which functions I could read up into using, and we'll see where it goes from there.
Someone has tried to work with the same dataset, albeit building this function with a slightly different purpose - that is, to get the full timetable of all trains running on a particular day (with each train departure/intermediate/terminating location as a row). The function is detailed here: https://github.com/jhumphry/ukraildata_etl/blob/master/sql/mca_get_full_timetable.sql


demo:db<>fiddle
You need a self-join on an ordered stop id (hope you have such a column). You have to join every journey with itself but only with the following stops:
SELECT
s1.journey_id,
s1.stop_name,
s2.stop_name
FROM
schedule s1
JOIN schedule s2 ON s1.journey_id = s2.journey_id AND s1.stop_id < s2.stop_id

Related

Is it possible to use SQL to show the average of some values in one column and then in subsequent columns display the individual values?

I have a bunch of data and I want the output to display an average of all the data points but also the individual data points in subsequent columns. Ideally it would look something like this:
Compound | Subject | Avg datapoint | Datapoint Experiment 1 | Datapoint Exp 2 | ...
..........XYZ......|.....ABC....|............40...............|...............20..............................|...............60...............|......
..........TUV......|.....ABC....|............30...............|...............20..............................|...............40...............|......
..........TUV......|.....DEF....|............20...............|...............10..............................|...............30...............|......
One problem I'm running in to is that I get repetitive lines of information. Another is that I have some rows pulling in info that doesn't apply, such that some of the individual datapoints in, say, row 2 would have info from subject DEF when I only want it to have info from subject ABC.
I hope this makes sense! I'm currently using inner join with a ton of where qualifiers. I'm close but not quite there. Any help is appreciate and let me know if I can provide additional info to help you help me.

The SQL language has a very strict rule requiring you to know the exact number of columns for your result set in advance, before looking at any data in your tables.
Therefore, if this average is based off a known fixed number of columns, or if the number of potential columns is reasonably small, where you can manually setup placeholders, then this will be possible. The key search terms to learn how to do this is "conditional aggregation", where you may also need to join the table to itself for each field.
Otherwise, you will need to pivot and aggregate your data in your client code or reporting tool.

How to populate all possible combination of values in columns, using Spark/normal SQL

I have a scenario, where my original dataset looks like below
Data:
Country,Commodity,Year,Type,Amount
US,Vegetable,2010,Harvested,2.44
US,Vegetable,2010,Yield,15.8
US,Vegetable,2010,Production,6.48
US,Vegetable,2011,Harvested,6
US,Vegetable,2011,Yield,18
US,Vegetable,2011,Production,3
Argentina,Vegetable,2010,Harvested,15.2
Argentina,Vegetable,2010,Yield,40.5
Argentina,Vegetable,2010,Production,2.66
Argentina,Vegetable,2011,Harvested,15.2
Argentina,Vegetable,2011,Yield,40.5
Argentina,Vegetable,2011,Production,2.66
Bhutan,Vegetable,2010,Harvested,7
Bhutan,Vegetable,2010,Yield,35
Bhutan,Vegetable,2010,Production,5
Bhutan,Vegetable,2011,Harvested,2
Bhutan,Vegetable,2011,Yield,6
Bhutan,Vegetable,2011,Production,3
Image of the above csv:
Now there is a very small country lookup table which has all possible countries the source data can come with, listed. PFB:
I want to have the output data's number of columns always fixed (this is to ensure the reporting/visualization tool doesn't get dynamic number columns with every day's new source data ingestions depending on the varying distinct number of countries present).
So, I've to somehow join the source data with the country_lookup csv and populate all those columns with default value as F. Every country column would be binary with T or F being the possible values.
The original dataset from the above has to be converted into below:
Data (I've kept the Amount field unsolved for column Type having Derived Yield as is, rather than calculating them below for a better understanding and for you to match with the formulae):
Country,Commodity,Year,Type,Amount,US,Argentina,Bhutan,India,Nepal,Bangladesh
US,Vegetable,2010,Harvested,2.44,T,F,F,F,F,F
US,Vegetable,2010,Yield,15.8,T,F,F,F,F,F
US,Vegetable,2010,Production,6.48,T,F,F,F,F,F
US,Vegetable,2010,Derived Yield,(2.44+15.2)/(6.48+2.66),T,T,F,F,F,F
US,Vegetable,2010,Derived Yield,(2.44+7)/(6.48+5),T,F,T,F,F,F
US,Vegetable,2010,Derived Yield,(2.44+15.2+7)/(6.48+2.66+5),T,T,T,F,F,F
US,Vegetable,2011,Harvested,6,T,F,F,F,F,F
US,Vegetable,2011,Yield,18,T,F,F,F,F,F
US,Vegetable,2011,Production,3,T,F,F,F,F,F
US,Vegetable,2011,Derived Yield,(6+10)/(3+9),T,T,F,F,F,F
US,Vegetable,2011,Derived Yield,(6+2)/(3+3),T,F,T,F,F,F
US,Vegetable,2011,Derived Yield,(6+10+2)/(3+9+3),T,T,T,F,F,F
Argentina,Vegetable,2010,Harvested,15.2,F,T,F,F,F,F
Argentina,Vegetable,2010,Yield,40.5,F,T,F,F,F,F
Argentina,Vegetable,2010,Production,2.66,F,T,F,F,F,F
Argentina,Vegetable,2010,Derived Yield,(2.44+15.2)/(6.48+2.66),T,T,F,F,F,F
Argentina,Vegetable,2010,Derived Yield,(15.2+7)/(2.66+5),F,T,T,F,F,F
Argentina,Vegetable,2010,Derived Yield,(2.44+15.2+7)/(6.48+2.66+5),T,T,T,F,F,F
Argentina,Vegetable,2011,Harvested,10,F,T,F,F,F,F
Argentina,Vegetable,2011,Yield,90,F,T,F,F,F,F
Argentina,Vegetable,2011,Production,9,F,T,F,F,F,F
Argentina,Vegetable,2011,Derived Yield,(6+10)/(3+9),T,T,F,F,F,F
Argentina,Vegetable,2011,Derived Yield,(10+2)/(9+3),F,T,T,F,F,F
Argentina,Vegetable,2011,Derived Yield,(6+10+2)/(3+9+3),T,T,T,F,F,F
Bhutan,Vegetable,2010,Harvested,7,F,F,T,F,F,F
Bhutan,Vegetable,2010,Yield,35,F,F,T,F,F,F
Bhutan,Vegetable,2010,Production,5,F,F,T,F,F,F
Bhutan,Vegetable,2010,Derived Yield,(2.44+7)/(6.48+5),T,F,T,F,F,F
Bhutan,Vegetable,2010,Derived Yield,(15.2+7)/(2.66+5),F,T,T,F,F,F
Bhutan,Vegetable,2010,Derived Yield,(2.44+15.2+7)/(6.48+2.66+5),T,T,T,F,F,F
Bhutan,Vegetable,2011,Harvested,2,F,F,T,F,F,F
Bhutan,Vegetable,2011,Yield,6,F,F,T,F,F,F
Bhutan,Vegetable,2011,Production,3,F,F,T,F,F,F
Bhutan,Vegetable,2011,Derived Yield,(2.44+7)/(6.48+5),T,F,T,F,F,F
Bhutan,Vegetable,2011,Derived Yield,(10+2)/(9+3),F,T,T,F,F,F
Bhutan,Vegetable,2011,Derived Yield,(6+10+2)/(3+9+3),T,T,T,F,F,F
The image of the above expected output data for a structured look at it:
Part 1 -
Part 2 -
Formulae for populating Amount Field for Derived Type:
Derived Amount = Sum of Harvested of all countries with T (True) grouped by Year and Commodity columns divided by Sum of Production of all countries with T (True)grouped by Year and Commodity columns.
So, the target is to have a combination of all the countries from source and calculate the sum of respective Harvested and Production values which then has to be divided. The commodity can be more than one in the actual scenario for any given country, but that should not bother as the summation of amount happens on grouped commodity and year.
Note: The users in the frontend can select any combination of countries. The sole purpose of doing it in the backend rather than dynamically doing it in the frontend is because AWS QuickSight (our visualisation tool), even though can populate sum on selected column filters but doesn't yet support calculation on those derived summed fields. Hence, the entire calculation of all combination of countries has to be pre-populated (very naive approach) in order to make it available in report on dynamic users selection of countries.
Also if you've any better approach (than the above naive approach mentioned in note) to solve this problem, you are most welcome to guide me. I've also posted a question on the same problem without writing my expected approach for experts to show me the path on how we can solve this kind of a problem better than this naive approach. If you want to help solve it with some other technique, you're most welcome, here is the link to that question.
Any help shall be greatly acknowledged.

Tableau count values after a GROUP BY in SQL

I'm using Tableau to show some schools data.
My data structure gives a table that has all de school classes in the country. The thing is I need to count, for example, how many schools has Primary and Preschool (both).
A simplified version of my table should look like this:
In that table, if I want to know the number needed in the example, the result should be 1, because in only one school exists both Primary and Preschool.
I want to have a multiple filter in Tableau that gives me that information.
I was thinking in the SQL query that should be made and it needs a GROUP BY statement. An example of the consult is here in a fiddle: Database example query
In the SQL query I group by id all the schools that meet either one of the conditions inside de IN(...) and then count how many of them meet both (c=2).
Is there a way to do something like this in Tableau? Either using groups or sets, using advanced filters or programming a RAW SQL calculated fiel?
Thanks!
Dubafek
PS: I add a link to my question in Tableu's forum because you can download my testing workbook there: Tableu's forum question

I've solved the issue using LODs (specifically INCLUDE and EXCLUDE statements).
I created two calculated fields having the aggregation I needed:
Then I made a calculated field that leaves only the School IDs that matches the number of types they have (according with the filtering) with the number of types selected in the multiple filter (both of the fields shown above):
Finally, I used COUNTD([Condition]) to display the amounts of schools matching with at least the School types selected.
Hope this helps someone with similar issue.
PS: If someone wants the Workbook with the solution I've uploaded it in an answer in the Tableau Forum

Merge two CSV and collate data

I have two CSV files, the first like so:
Book1:
ID,TITLE,SUBJECT
0001,BLAH,OIL
0002,BLAH,HAMSTER
0003,BLAH,HAMSTER
0004,BLAH,PLANETS
0005,BLAH,JELLO
0006,BLAH,OIL
0007,BLAH,HAMSTER
0008,BLAH,JELLO
0009,BLAH,JELLO
0010,BLAH,HAMSTER
0011,BLAH,OIL
0012,BLAH,OIL
0013,BLAH,OIL
0014,BLAH,JELLO
0015,BLAH,JELLO
0016,BLAH,HAMSTER
0017,BLAH,PLANETS
0018,BLAH,PLANETS
0019,BLAH,HAMSTER
0020,BLAH,HAMSTER
And then a second CSV with items associated with the first list, with ID being the common attribute between the two.
Book2:
ID,ITEM
0001,PURSE
0001,STEAM
0001,SEASHELL
0002,TRUMPET
0002,TRAMPOLINE
0003,PURSE
0003,DOLPHIN
0003,ENVELOPE
0004,SEASHELL
0004,SERPENT
0004,TRUMPET
0005,CAR
0005,NOODLE
0006,CANNONBALL
0006,NOODLE
0006,ORANGE
0006,SEASHELL
0007,CREAM
0007,CANNONBALL
0007,GUM
0008,SERPENT
0008,NOODLE
0008,CAR
0009,CANNONBALL
0009,SERPENT
0009,GRAPE
0010,SERPENT
0010,CAR
0010,TAPE
0011,CANNONBALL
0011,GRAPE
0012,ORANGE
0012,GUM
0012,SEASHELL
0013,NOODLE
0013,CAR
0014,STICK
0014,ORANGE
0015,GUN
0015,GRAPE
0015,STICK
0016,BASEBALL
0016,SEASHELL
0017,CANNONBALL
0017,ORANGE
0017,TRUMPET
0018,GUM
0018,STICK
0018,GRAPE
0018,CAR
0019,CANNONBALL
0019,TRUMPET
0019,ORANGE
0020,TRUMPET
0020,CHERRY
0020,ORANGE
0020,GUM
The real datasets are millions of records, so I'm sorry in advance for my simple example.
The problem I need to solve is getting the data merged and collated in a way where I can see which item groupings most commonly appear together on the same ID. (e.g. GRAPE,GUM,SEASHELL appear together 340 times, ORANGE and STICK 89 times, etc...)
Then I need to see if there is any change/deviation to the general results in common appearance when grouped by SUBJECT.
Tools I'm familiar with are Excel and SQL, but I also have PowerBI and Alteryx at my disposal.
Full disclosure: Not homework, or work, but a volunteer project, thus my unfamiliarity with this kind of data manipulation.
Thanks in advance.

An Alteryx solution:
Drag the two .csv files onto your canvas (seen as book1.csv and book2.csv in my picture; Alteryx will create "Input" tools for you.
Drag a "Join" tool on and connect the two .csv files to its inputs; select "ID" as the join field; unselect the "Right_ID" as output since it's merely a duplicate of "ID"
Drag a "Summary" tool on and connect the Join tool's output to the Summary tool's input; select all three of the outputs and add as a "group by"... then add the ID column with a "count"
Drag a browse tool on and connect the summary's output to the browse tool's input.
run the workflow
After all that, click on the browse tool and you should see what is seen in my screenshot: (which is showing just the first ten rows of output):

+1 for taking on a volunteer project - I think anyone who knows data can have a big impact in support of their favourite group or cause.
I would just pull the 2 files into Power BI as 2 separate tables (Get Data / From File). Create a relationship between the 2 tables based on ID (it might get auto-generated). It should be one to many.
Then I would add a Calculated Column to the Book1 table to Concatenate the related ITEM values, eg.
Items =
CALCULATE (
CONCATENATEX (
DISTINCT ( 'Book2'[ITEM] ),
'Book2'[ITEM],
", ",
'Book2'[ITEM], ASC
)
)
Now you can use that Items field in visuals (e.g. a Table), along with Count of ID to get the frequency.
Adding Subject to a copy of the table (e.g. to the Columns well of a Matrix) will produce your grouped scenario, or you could add a Subject Slicer.
As you will be comparing subsets of varying size, I would change Count of ID to Show value as - % of grand total.

Little different solution using Alteryx.
With this dataset, there are very few repeating 3 or 4 item groups. You can do the two item affinity analysis and get a probability of 3 or 4 item groups, or you can count the 3 and 4 item groups individually. I believe what you want is the latter as your probability of getting grapes with oranges may be altered by whether you have bananas in the cart or not.
Anyway, I did not join in the subject until after finding all of my combinations. I found all the combinations by taking the Cartesian join of two, then three, then four of the original set. I then removed all duplicates by ensuring items were always in alphabetical order in each row. I then counted occurrences of each combination. More joins can be added in the same pattern to count groups of 5,6,7...
Once you have the counts of occurrences, then I would join back with the subjects and perform this analysis on each group and compare to the overall results.
I'm supposed to disclose that I work for Alteryx.

first of all if you are using windows
just navigate to the directory which contains the CSV and write the following command:
copy pattern newfileName.csv
#example
copy *.csv merged.csv
now you created one csv file, the file is too large now you can't process it once, depending on your programming language you can use appropriate way, for python you can use generators to process line by line, or pandas you can read chunk by chunk it will be easy.
I hope this help you.

Two Dimensional Diagram with aggr function

I'm having a very curious Problem in QlikView.
I have a number of readouts from a Database which show certain amounts of time in a different state.
In that table there are 49 variables that describe the state, there are 7 levels of i.e the SOC and seven states of the Temperature.
i.e the one of the fields could be named: SOC1_T1 or SOC2_T1 and so on...
So what i get is a table full of readouts in which every i have an specific id for the object, the state of the variables and an age. There are multiple entries per Object.
What i want to do is to plot a two dimensional diagram over all the states so i get SOC over Temperatur Histogram(Average of the maximum (or newest) value of every object).
I tried creating to Dynamic (or syntethic) Dimensions (ValueLoop(1,7) and ValueLoop(1,8).
In the formulas i reffered to them with
=If(ValueLoop(1,7) = 1 and ValueLoop(1,8) = 1,
(avg(aggr(FirstSortedValue (SOC1_T1
, -age), id)) * 100))
and created 49 Formulas with each state variable output.
Problem now is:
It only shows the first entry. I can replace the whole expression in the if condition with a specific number (100) and get a result. I also plotted the inner expression into a Listbox and checked wheter the result is not null.
As soon as I delete the aggr function and just take the AVG over everything (which is not what i want). Everything works fine. When i turn back to aggr, only the first one is shown.
Doesnt help by the way when i delete one of the dimensions, this doesnt work one dimensional either.
Any ideas or workarounds?
Greetings
Julian