Recursive CTE generating extra record - sql-server

Question

I have following Recursive SQL query to generate all dates for any month provided in a date.
It always generate extra date(1st of next month).
DECLARE #currentDate DATE = '2016-5-25';
WITH cte AS(
SELECT DATEADD(DAY, -DATEPART(DAY, #currentDate) + 1, #currentDate) AS firstDay
UNION ALL
SELECT DATEADD(DAY, 1, firstDay)
FROM cte
WHERE DATEPART(MONTH, firstDay) = DATEPART(MONTH, #currentDate)
)
SELECT * FROM cte
What am I doing wrong?

Answer 1

In Recursive CTE, the recursive query will be first executed then the Where clause is validated
Here is the correct way
DECLARE #currentDate DATE = '2016-5-25';
;WITH cte AS(
SELECT dateadd(dd,1,eomonth(#currentDate,-1)) AS fd
UNION ALL
SELECT DATEADD(DAY, 1, fd)
FROM cte
WHERE fd < eomonth(#currentDate)
)
SELECT * FROM cte
Instead you can use tally table to do this which is way better in performance when compared to Recursive CTE
;WITH e1(n) AS
(
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1
), -- 10
e2(n) AS (SELECT 1 FROM e1 CROSS JOIN e1 AS b), -- 10*10
e3(n) AS (SELECT 1 FROM e1 CROSS JOIN e2), -- 10*100
tally as (SELECT id = ROW_NUMBER() OVER (ORDER BY n) FROM e3 )
select
dateadd(DD,ID-1,dateadd(dd,1,eomonth(#currentDate,-1))) as Dates
from Tally
where dateadd(DD,ID-1,dateadd(dd,1,eomonth(#currentDate,-1)))<=eomonth(#currentDate)