I am unable to figure out how to make a column values into column headers and assign appropriate values as it happens
Say I have a Postgres database with the following table:
Name Subject Score Region
======= ========= ======= =======
Joe Chemistry 20 America
Robert Math 30 Europe
Jason Physics 50 Europe
Joe Math 70 America
Robert Physics 80 Europe
Jason Math 40 Europe
Jason Chemistry 60 Europe
I want to select/fetch data in the following form:
Name Chemistry Math Physics Region
======= ========== ======= ======== ========
Joe 20 70 null America
Robert null 30 80 Europe
Jason 60 40 50 Europe
Considering that there are 80 subjects. How do I write an SQL select statement that returns data in this format?
In Postgres, I recommend using the FILTER syntax for conditional aggregation:
SELECT name,
MAX(score) FILTER (WHERE subject = 'Chemistry') AS Chemistry,
MAX(score) FILTER (WHERE subject = 'Math') AS Math,
MAX(score) FILTER (WHERE subject = 'Physics') AS Physics
FROM grades
GROUP BY name
Related
I am using ScaNN to perform similarity searches and would like to place more emphasis on some features than others when performing a similarity search.
for example, if I have the following data
name | age | country | income
John 29 US $47k
Susan 28 US $44k
Bill 26 US $39k
Sarah 35 UK $100k
Jack 34 UK $90k
Maggie 37 UK $95k
and income has more importance, then given the following query:
George, 28, US, $100k
it would return
Sarah, Jack, Maggie
adding more weight to the income feature.
Training data values are normalized before building the similarity index
df_np = preprocessing.normalize(df[features])
and likewise the query values are normalized before performing a search
np_q = preprocessing.normalize([list(query.values())])
Students table
student_id student_name
1 John
2 Mary
Grades table
student_id year grade_level school Course Mark
1 2015 10 Smith High Algebra 95
1 2015 10 Smith High English 96
1 2016 11 Smith High Geometry 85
1 2016 11 Smith High Science 88
2 2015 10 Smith High Algebra 98
2 2015 10 Smith High English 93
2 2016 11 Smith High Geometry 97
2 2016 11 Smith High Science 86
I'm trying to show results for each year and what class a student took with the grade.
So the final output i'm looking for is something like:
[student_id1] [year1] [grade1] [school1]
[course1] [mark1]
[course2] [mark2]
[course3] [mark3]...
[student_id1] [year2] [grade2] [school1]
[course1] [mark1]
[course2] [mark2]
[course3] [mark3]...
[student_id2] [year1] [grade1] [school1]
[course1] [mark1]
[course2] [mark2]
[course3] [mark3]...
This would all go in one column/row. So in this particular example, this would be my result:
1 2015 10 Smith High
Algebra 95
English 96
1 2016 11 Smith High
Geometry 85
Science 88
2 2015 10 Smith High
Algebra 98
English 93
2 2016 11 Smith High
Geometry 97
Science 86
So anytime a student id, year, grade, or school name changes, I would have a line for that and loop through the classes taken within that group. And all of this would be in one column/row.
This is what I have so far but I'm not sure how I can properly loop through course and grades for each group. I'd appreciate it if I can be pointed in the right direction.
select s.student_id + '' + year + '' + grade_level + '' + school
from students
join grades on students.student_id = grades.student_id
If you want to do it in your SQL Enviromnment, it depends on the Database Management System you are using.
For example, if you are using Transact SQL you can try to look at this link.
Generally this kind of loops and interactions are done in the programming language that is coupled with the SQL DB.
Anyway, you should look at Stored Procedures and Cursors if you really want to do this in SQL.
You are trying to mix presentation with retrieval of data from database tables. Looping through the resultset in sql can be achieved via cursor but that isn't adviced. You are better off by pulling the required data using two queries and later print it using a language of your choice.
Let's say there's a table called Winner, with 3 attributes: Name, Gender and Id.
Name Gender Id
Kevin Male 8
Kevin Male 8
Benny Male 31
Jenny Female 7
Louie Male 4
Peter Male 11
Kevin Male 2
Jenny Female 7
Jenny Female 7
Chris Male 23
Louie Female 14
Apart from those people who is actually 2 different person but with the same name and those people who have the same name but with different gender, their Id's will be the unique value to identify themselves. If I want to list all the Id's who appeared once only in the list, I am thinking to do something like this:
Am I expressing it correctly ?
I don't know what your formula is trying to say, but in SQL you can achieve the result you want with a GROUP BY query:
SELECT Id, COUNT(Id) AS idCount
FROM Winner
GROUP BY Id
HAVING COUNT(Id) = 1
I have one table:
Person Name Country code
Andrew 1
Philip 2
John 1
Daniel 2
and a lookup table:
Country code Country name
1 USA
2 UK
I added them to powerpivot, created a relationship between the country code fields, then I created a pivot table. I expect to get the following:
Person Name Country code
Andrew USA
Philip UK
John USA
Daniel UK
But what I actually get is:
Person Name Country code
Andrew USA
Andrew UK
Philip USA
Philip UK
John USA
John UK
Daniel USA
Daniel UK
Couple of options:
Add a column to your main table that uses a formula to pull in the Country Name from your LookUp Table e.g.
=RELATED(LookUpTable[Country Name])
If you drag in any measure that references the main table you will get your desired result e.g. =COUNTROWS('MainTable') You then hide the results column if you had to.
I am trying to return the country, golfer name, golfer age, and average drive for the golfers with the highest average drive from each country.
However I am getting a result set with duplicates of the same country. What am I doing wrong? here is my code:
select distinct country, name, age, avgdrive
from pga.golfers S1
inner join
(select max(avgdrive) as MaxDrive
from pga.golfers
group by country) S2
on S1.avgdrive = s2.MaxDrive
order by avgdrive;
These are some of the results I've been getting back, I should only be getting 15 rows, but instead I'm getting 20:
COUN NAME AGE AVGDRIVE
---- ------------------------------ ---------- ----------
Can Mike Weir 35 279.9
T&T Stephen Ames 41 285.8
USA Tim Petrovic 39 285.8
Ger Bernhard Langer 47 289.3
Swe Fredrik Jacobson 30 290
Jpn Ryuji Imada 28 290
Kor K.J. Choi 37 290.4
Eng Greg Owen 33 291.8
Ire Padraig Harrington 33 291.8
USA Scott McCarron 40 291.8
Eng Justin Rose 25 293.1
Ind Arjun Atwal 32 293.7
USA John Rollins 30 293.7
NIr Darren Clarke 37 294
Swe Daniel Chopra 31 297.2
Aus Adam Scott 25 300.6
Fij Vijay Singh 42 300.7
Spn Sergio Garcia 25 301.9
SAf Ernie Els 35 302.9
USA Tiger Woods 29 315.2
You are missing a join condition:
select s1.country, s1.name, s1.age, s1.avgdrive
from pga.golfers S1 inner join
(select country, max(avgdrive) as MaxDrive
from pga.golfers
group by country
) S2
on S1.avgdrive = s2.MaxDrive and s1.country = s2.country
order by s1.avgdrive;
Your problem is that some people in one country have the same average as the best in another country.
DISTINCT eliminated duplicate rows, not values in some fields.
To get a list of countries with ages, names, and max drives, you would need to group the whole select by country.