SQL | View Column as Multiple Columns Based on Conditions - sql

Question

Newbie Postgresql (9.6.6) question here :)
I want to create a View that will split a single column into several columns, based on different conditions.
Example Table
Name Score Season
------- ------- --------
John 12 Fall
John 15 Winter
John 13 Spring
Sally 17 Fall
Sally 10 Winter
Sally 14 Spring
Henry 16 Fall
Henry 12 Winter
Henry 18 Spring
I want the View to dislay something that looks like this:
Name Fall Score Winter Score Spring Score
------- ------------ -------------- --------------
John 12 15 13
Sally 17 10 14
Henry 16 12 18
Where the "Score" field is broken out into several different columns, each one populated based on WHERE clause that references the "Season" field. I've looked into both Window Functions and CASE Statements for accomplishing this purpose, but haven't been successfully thus far.
Any help is greatly appreciated!

Answer 1

Selecting from the entire table while grouping over the Name and then conditionally SUMming over the Score column will work:
SELECT
"Name",
SUM(CASE WHEN "Season" = 'Fall' THEN "Score" ELSE 0 END) AS "Fall",
SUM(CASE WHEN "Season" = 'Winter' THEN "Score" ELSE 0 END) AS "Winter",
SUM(CASE WHEN "Season" = 'Spring' THEN "Score" ELSE 0 END) AS "Spring"
FROM "mytable"
GROUP BY "Name"
Whether or not you use SUM() is up to you and how your data looks. If you have one row per (Name, Season) pair then SUM() will work equally as well as MAX()

Answer 2

You need a pivot table:
On SQL server you can do something like this example (hope it's the same for postgress), in others versions of SQL exist the pivot relational operators, but I'm not sure if Pivot works on Postgres
Example:
CREATE TABLE #Table
(
Name nvarchar(400),
Score int,
Season nvarchar(400)
)
insert into #Table values ( 'John ',12,'Fall')
insert into #Table values ( 'John ',15,'Winter' )
insert into #Table values ( 'John ',13,'Spring' )
insert into #Table values ( 'Sally',17,'Fall ' )
insert into #Table values ( 'Sally',10,'Winter' )
insert into #Table values ( 'Sally',14,'Spring' )
insert into #Table values ( 'Henry',16,'Fall' )
insert into #Table values ( 'Henry',12,'Winter' )
insert into #Table values ( 'Henry',18,'Spring' )
select
c.Name
,sum(c.[Fall Score]) as [Fall Score]
,sum(c.[Winter Score]) as [Winter Score]
,sum(c.[Spring Score]) as [Spring Score]
from
(SELECT
t.name,
case
when t.Season = 'Fall' then t.Score
when t.Season = 'Winter' then 0
when t.Season = 'Spring' then 0
end as [Fall Score],
case
when t.Season = 'Fall' then 0
when t.Season = 'Winter' then t.Score
when t.Season = 'Spring' then 0
end as [Winter Score],
case
when t.Season = 'Fall' then 0
when t.Season = 'Winter' then 0
when t.Season = 'Spring' then t.Score
end as [Spring Score]
from #Table t
)as c
group by c.name