SQL Query to make dynamic columns - sql

Question

Hi I have a query that gets the total count of incidents per month and year
I wanted a result that shows all distinct years in columns
Could you please advise how to make this query dynamic?
Expected Result:
Month 2013 2014 2015
January 8 0 12
February 9 6 10
March 12 1 9
April 10 13 27
May 9 22 15
June 27 4 20
July 15 12 22
August 20 2 2
September 22 5 10
October 10 8 12
November 0 7 0
December 0 15 0
Query
select DATENAME(MONTH,DateOpened) as Month,
sum(case when year(DateOpened) = '2015' then 1 else 0 end) as [2015],
sum(case when year(DateOpened) = '2014' then 1 else 0 end) as [2014]
from Incidents
group by DATENAME(MONTH,DateOpened), MONTH(DateOpened)
order by MONTH(DateOpened)
Thanks for your help!

Answer 1

You can use the PIVOT table operator instead, something like this:
SELECT *
FROM
(
SELECT
DATENAME(MONTH,DateOpened) as Month,
DATENAME(Year,DateOpened) AS Year,
DateOpened
FROM Incidents
) AS t
PIVOT
(
COUNT(DateOpened)
FOR Year IN([2013], [2014], [2015])
) AS p;
SQL Fiddle Demo
If you don't need to write the list of years and do it dynamically for any year, you have to use dynamic SQL to run the query dynamically, like this:
DECLARE #cols AS NVARCHAR(MAX);
DECLARE #query AS NVARCHAR(MAX);
SELECT #cols = STUFF((SELECT distinct ',' +
QUOTENAME(DATENAME(Year,DateOpened))
from Incidents AS t
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
, 1, 1, '');
SELECT #query = 'SELECT * , '+ #cols + '
FROM
(
select
DATENAME(MONTH,DateOpened) as Month,
DATENAME(Year,DateOpened) AS Year,
DateOpened
FROM Incidents
) AS t
PIVOT
(
COUNT(DateOpened)
FOR Year IN(' + #cols + ')' +
') p';
execute(#query);
SQL Fiddle Demo
This will give you something like this:
| Month | 2014 | 2015 | 2014 | 2015 |
|-----------|------|------|------|------|
| April | 0 | 3 | 0 | 3 |
| August | 1 | 1 | 1 | 1 |
| December | 1 | 0 | 1 | 0 |
| February | 0 | 1 | 0 | 1 |
| July | 1 | 1 | 1 | 1 |
| September | 1 | 0 | 1 | 0 |
Note that: Both the queries won't list any month that has no dates on the original table. If you want to list any month that is not listed on the table with counts 0, you have to modify the anchor query so that it lists all the months even if not listed:
SELECT
m.Name as Month,
i.Year,
i.DateOpened
FROM
(
VALUES ('Janurary'), ('February'), ('March'),
('April'), ('May'), ('June'),
('July'), ('August'), ('September'),
('October'), ('November'), ('December')
) AS m(Name)
LEFT JOIN
(
SELECT
DATENAME(MONTH,DateOpened) as Month,
DATENAME(Year,DateOpened) AS Year,
DateOpened
FROM Incidents
) AS i ON i.Month = m.Name
and replace it in the dynamic query.
Updated SQL Fiddle
This will give you the missing months with zeros results:
| Month | 2014 | 2015 | 2014 | 2015 |
|-----------|------|------|------|------|
| Janurary | 0 | 0 | 0 | 0 | <<
| February | 0 | 1 | 0 | 1 |
| March | 0 | 0 | 0 | 0 | <<
| April | 0 | 3 | 0 | 3 |
| May | 0 | 0 | 0 | 0 | <<
| June | 0 | 0 | 0 | 0 | <<
| July | 1 | 1 | 1 | 1 |
| August | 1 | 1 | 1 | 1 |
| September | 1 | 0 | 1 | 0 |
| October | 0 | 0 | 0 | 0 | <<
| November | 0 | 0 | 0 | 0 | <<
| December | 1 | 0 | 1 | 0 |

Answer 2

A simple create table something like this..
CREATE TABLE #tmpIncidents
(
IncidentName NVARCHAR(50)
, DateOpened DATETIME
)
INSERT INTO #tmpIncidents (IncidentName,DateOpened) VALUES
('Test1',GETDATE()),
('Test1',DATEADD(YEAR,-1,GETDATE())),
('Test1',DATEADD(YEAR,-2,GETDATE())),
('Test1',DATEADD(YEAR,2,GETDATE())),
('Test1',DATEADD(YEAR,1,GETDATE())),
('Test1',DATEADD(YEAR,3,GETDATE()))
Then a build up query for multiple years
DECLARE #columnVar NVARCHAR(4000)
SELECT #columnVar =
(SELECT DISTINCT
'[' + CONVERT(NVARCHAR(150),DATEPART(YEAR,DateOpened)) + '],' AS [text()]
FROM #tmpIncidents
FOR XML PATH('')
)
SET #columnVar = (SELECT LEFT(#columnVar,LEN(#columnVar)-1))
--SELECT #columnVar --so you can see how it looks..
Then execute your query.
EXEC ('
SELECT
pv.*
FROM
(
SELECT DATENAME(MONTH,DateOpened) AS [DateName], DATEPART(YEAR,DateOpened) AS [YEAR], IncidentName FROM #tmpIncidents
) src
PIVOT
(
COUNT(IncidentName)
FOR [YEAR] IN (' + #columnVar + ')
) pv;
')