Select unexist date yyyy/mm - sql

Question

I have a SQL query as follows:
SELECT
R.BOOK_YM, COUNT(*)
FROM
#TB_TRANSED_GUI_AMOUNT AS R
GROUP
BY R.BOOK_YM
The selected results like as follows:
BOOK_YM | count(*)
---------+---------
201411 | 51
201412 | 142
201501 | 1
201506 | 1
How do I modify the result like the follows:
BOOK_YM | count(*)
--------+-----------
201411 | 51
201412 | 142
201501 | 1
201502 | 0
201503 | 0
201504 | 0
201505 | 0
201506 | 1

Answer 1

You can use the following to get a table of all YYYYMM between 2 dates and use the resulting #YMList variable in a join:
declare #StartDate date = cast(dateadd(month, -12, GetDate()) as date)
declare #EndDate date = cast(GetDate() as date)
declare #YMList TABLE (YYYYMM INT)
;with dates as (
SELECT cast(#StartDate as Date) [date]
UNION ALL
SELECT DATEADD(month,1,t.date)
FROM dates t
WHERE t.[date] < #EndDate
)
insert #YMList (YYYYMM)
select
YEAR([Date]) * 100 + MONTH([Date]) AS YYYYMM
from dates
WHERE [Date] < #EndDate
OPTION (MAXRECURSION 10000)

Answer 2

Try this: (I think BOOK_YM is a varchar field if not CAST it)
SELECT
Y.YYYY + M.MM AS BOOK_YM,
COUNT(R.BOOK_YM) AS CNT
FROM
(SELECT SUBSTRING(BOOK_YM, 1, 4) As YYYY
FROM t
GROUP BY SUBSTRING(BOOK_YM, 1, 4)) AS Y
CROSS JOIN
(SELECT '01' As MM
UNION ALL SELECT '02'
UNION ALL SELECT '03'
UNION ALL SELECT '04'
UNION ALL SELECT '05'
UNION ALL SELECT '06'
UNION ALL SELECT '07'
UNION ALL SELECT '08'
UNION ALL SELECT '09'
UNION ALL SELECT '10'
UNION ALL SELECT '11'
UNION ALL SELECT '12') AS M
LEFT JOIN
t AS R
ON Y.YYYY + M.MM = R.BOOK_YM
WHERE
Y.YYYY + M.MM BETWEEN (SELECT MIN(BOOK_YM) FROM t) AND (SELECT MAX(BOOK_YM) FROM t)
GROUP BY
Y.YYYY + M.MM