SQL Union in Separate Columns - sql

Question

I made a database to enter all my headache and migraine tracking data into. I'm pulling some queries that show counts of different headache severity by month for a certain year. I have one query that gets all headaches by month, another gets headaches under a certain severity, and the last gets headaches over a certain severity. There are two columns I'm using in the database: HeadacheDate and Severity. I'd like to do a query that would have the following columns as output:
Month, Count of All Headaches, Count of Headaches under 6 Severity,
Count of Headaches Over 5 Severity
I've made a union query that takes 3 queries and gives me the data I want but I just can't figure out how to do a query that will move the data around to give me the column format I want.
Here are my union queries:
SELECT
DateName(month, DateAdd(month, MONTH(HeadacheDate), -1)) AS
HeadacheMonth,
COUNT(Severity) as SeverityCount
FROM
Headaches
WHERE
Severity > 0 AND YEAR(HeadacheDate) = 2013
GROUP BY
MONTH(HeadacheDate)
UNION
SELECT
DateName(month, DateAdd(month, MONTH(HeadacheDate), -1)) AS HeadacheMonth,
COUNT(Severity) as SeverityCount
FROM
Headaches
WHERE
Severity > 0 AND Severity < 6 AND YEAR(HeadacheDate) = 2013
GROUP BY
MONTH(HeadacheDate)
UNION
SELECT
DateName(month, DateAdd(month, MONTH(HeadacheDate), -1)) AS HeadacheMonth,
COUNT(Severity) as SeverityCount
FROM
Headaches
WHERE
Severity > 5 AND YEAR(HeadacheDate) = 2013
GROUP BY
MONTH(HeadacheDate);
This returns results something like this:
April 3
April 11
April 14
August 5
August 10
August 15
December 2
December 11
December 13
July 5
July 6
July 11
June 4
June 10
June 14
March 1
March 2
March 3
May 5
May 8
May 13
November 1
November 13
November 14
October 4
October 9
October 13
September 4
September 10
September 14
What I want is this:
Month, Count of All Headaches, Count of Headaches under 6 Severity, Count of Headaches Over 5 Severity
January, 20, 15, 5
February, 18, 13, 5
and so on.
I'd also like to include months where one of the count fields could be zero.

Answer 1

You can use conditional grouping:
SELECT
[HeadacheMonth] = DATENAME(month, DateAdd(month , MONTH(HeadacheDate), -1))
,[SeverityCountTotal] = COUNT(CASE WHEN Severity > 0 THEN 1 END)
,[SeverityCount_1_5] = COUNT(CASE WHEN Severity > 0
AND Severity < 6 THEN 1 END)
,[SeverityCount_6] = COUNT(CASE WHEN Severity > 5 THEN 1 END)
FROM Headaches
WHERE YEAR(HeadacheDate) = 2013
GROUP BY MONTH(HeadacheDate);
YEAR(HeadacheDate) = 2013 is not SARGable so if index exits on that column query optimizer will skip it.You could consider using:
HeadacheDate >= '2013-01-01T00:00:00' AND HeadacheDate < '2014-01-01T00:00:00'

Answer 2

SELECT Month
,COUNT(Severity) AS ALL
,SUM(CASE WHEN Severity<6 THEN 1 ELSE 0 END) AS SevUn6
,SUM(CASE WHEN Severity>5 THEN 1 ELSE 0 END) AS SevOv5
FROM <table>
GROUP BY Month