Joining query results into one - tsql

Question

This is my table to track down the employees off days. This example is only for one person.
ID PID Year OffDays DayTypeNumber
------------------------------------------
1 1 2011 10 1
2 1 2011 5 2
3 1 2012 20 1
4 1 2012 3 2
I would like to write such a query that should only show one result for each year with additional column
Year OffDays(1) OffDays(2)
------------------------------------------
2011 10 5
2012 20 3

Answer 1

You can use the PIVOT function for this:
select year,
[1] [OffDays(1)],
[2] [OffDays(2)]
from
(
select year, offdays, daytypenumber
from yourtable
) src
pivot
(
sum(offdays)
for daytypenumber in([1], [2])
) piv
See SQL Fiddle with Demo
Result:
| YEAR | OFFDAYS(1) | OFFDAYS(2) |
----------------------------------
| 2011 | 10 | 5 |
| 2012 | 20 | 3 |
Or you can use an aggregate function with a CASE statement:
select year,
sum(case when daytypenumber = 1 then offdays end) [OffDays(1)],
sum(case when daytypenumber = 2 then offdays end) [OffDays(2)]
from yourtable
group by year
See SQL Fiddle with Demo
If you only have two types that you are comparing, then you can use subqueries:
select t1.year,
[OffDays(1)],
[OffDays(2)]
from
(
select sum(offdays) [OffDays(1)], year
from yourtable
where daytypenumber = 1
group by year
) t1
left join
(
select sum(offdays) [OffDays(2)], year
from yourtable
where daytypenumber = 2
group by year
) t2
on t1.year = t2.year
See SQL Fiddle with Demo
The above answers will work great, if you have a known number of values for DayTypeNumber, but if those are unknown then you can use dynamic SQL to generate the PIVOT:
DECLARE #cols AS NVARCHAR(MAX),
#colNames AS NVARCHAR(MAX),
#query AS NVARCHAR(MAX)
select #cols = STUFF((SELECT distinct ',' + QUOTENAME(DayTypeNumber)
from yourtable
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
select #colNames = STUFF((SELECT distinct ', ' + QUOTENAME(DayTypeNumber)
+' as [OffDays('+cast(DayTypeNumber as varchar(10))+')]'
from yourtable
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
set #query = 'SELECT year,' + #colNames + ' from
(
select year, offdays, daytypenumber
from yourtable
) x
pivot
(
sum(offdays)
for daytypenumber in (' + #cols + ')
) p '
execute(#query)
See SQL Fiddle with Demo
All of these will produce the same results:
| YEAR | OFFDAYS(1) | OFFDAYS(2) |
----------------------------------
| 2011 | 10 | 5 |
| 2012 | 20 | 3 |