sql : calculate the total birthday moth based on month - sql

Question

I want to code a query to calculate the total birthday moth based on month . Here is the sample data . Two person's bithday are April, 1980 .
How to write this query ?
John 02/21/1980
Peter 02/22/1980
Lucy 04/21/1980
------ result -----
01/1980 0
02/1980 2
03/1980 0
04/1980 1
05/1980 0
.....

Answer 1

You can loop for every months like this:
DECLARE #month INT
DECLARE #year INT
DECLARE #result TABLE (MonthYear varchar(7),BirthdaysCount INT)
SET #month = 1
SET #year = 1980
WHILE(#month < 13)
BEGIN
INSERT INTO #result
SELECT (CAST(#month as VARCHAR) + '/' + CAST(#year as VARCHAR)),
COUNT(*)
FROM test
WHERE MONTH(birth) = #month AND YEAR(birth) = #year
SET #month = #month + 1
END
select * from #result
See the fiddle: http://sqlfiddle.com/#!3/20692/2

Answer 2

In MySQL you would do this:
select concat(month(dob), '/', year(dob)) monthYear, count(*) cnt from t
group by monthYear
order by year(dob), month(dob)
However, in order to get the "missing dates" you'll have to generate data, because 01/1980 is not in any table, as far as I can see. Check this answer to see how.

Answer 3

how about this for sql-server
create table #temp
(
name varchar(50),
DOB datetime
)
insert into #temp values ('john', '2/21/1980')
insert into #temp values ('peter', '2/22/1980')
insert into #temp values ('lucy', '4/21/1980')
select convert(varchar(2), MONTH(DOB)) + '/' + Convert(varchar(4), YEAR(DOB)) as [MM/YYYY]
, count(*) as TotalCount
from #temp
group by convert(varchar(2), MONTH(DOB)) + '/' + Convert(varchar(4), YEAR(DOB))
drop table #temp
EDIT - This will get you all records for the dates included in the dates in the table. It will use the Min/Max Date in the table to get the date range, you then use this range to get the count of the birthdays in each month:
create table #temp
(
name varchar(50),
DOB datetime
)
insert into #temp values ('john', '2/21/1980')
insert into #temp values ('peter', '2/22/1980')
insert into #temp values ('lucy', '4/21/1980')
;with cte as
(
select min(DOB) as MinDate, max(DOB) as MaxDate
from #temp
union all
SELECT dateadd(mm, 1, t.MinDate), t.MaxDate
from cte t
where dateadd(mm, 1, t.MinDate) <= t.MaxDate
)
select convert(varchar(2), MONTH(c.MinDate)) + '/' + Convert(varchar(4), YEAR(c.MinDate))
, IsNull(t.TotalCount, 0) as TotalCount
from cte c
LEFT JOIN
(
SELECT convert(varchar(2), MONTH(DOB)) + '/' + Convert(varchar(4), YEAR(DOB)) as [MM/YYYY]
, count(*) as TotalCount
FROM #temp
group by convert(varchar(2), MONTH(DOB)) + '/' + Convert(varchar(4), YEAR(DOB))
) t
on convert(varchar(2), MONTH(C.MinDate)) + '/' + Convert(varchar(4), YEAR(C.MinDate))
= t.[MM/YYYY]
drop table #temp