Is there an way to Loop in SQL - sql

Question

I'm trying to create a monthly Forecasting process in SQL. I've created a query for Jan and wanted to see if it's possible to loop through each additional month and store the results in a Temporary table.
Logically, I would like to set #DMonth variable to 1, run the query, store/append the results into a temp table, loop...
set #DMonth variable to 2, run the query, store/append the results into a temp table, loop...
etc.. setting #DMonth sequentially until it reaches 12 and then exit the loop.
Example variable in query:
Declare #DMonth int;
set #DMonth = 1
I believe I need to set the Loop around the Setting to of the #DMonth variable.

Answer 1

Well, of course, you can loop in sql.The syntax is slightly different but similar and you can easily understand it if you know basic coding.However we can only use the while loop in sql.
The syntax is like shown Below.
while loop. we basically use
While (n < X) = //Condition
BEGIN

Answer 2

It's not clear what do you really want to do inside your loop, but here is how to loop through and save month in a temp table:
CREATE TABLE #temp(mon int);
Declare #StartDate DATETIME = '2016-09-01',
#EndDate DATETIME = '2017-01-31'
-- Now you have 12 months and you can use below query to loop through each month starting from January
WHILE (#StartDate <= #EndDate)
BEGIN
DECLARE #Month INT = Month(#StartDate) -- At the start of loop #Month is equal to 9
-- Save #Month to temp table in each repeat
INSERT INTO #temp (mon)
SELECT #Month;
SET #StartDate = DATEADD(MONTH, 1, #StartDate); -- this line adds 1 value to #Month after first loop #Month will be 10
END
If you want to start your loop from #StartDate (September 2016) and then end it in #EndDate (January 2017) the above query does the exact same process. But if you want to change your #StartDate to 2016-01-01 and #EndDate to 2016-12-31 then use below query:
CREATE TABLE #temp(mon int);
Declare #StartDate DATETIME = DATEADD(MONTH, -8, '2016-09-01'); -- It will set #StartDate to '2016-01-01'
Declare #EndDate DATETIME = DATEADD(MONTH, 11, DATEADD(YEAR, -1, '2017-01-31')); -- It will set #EndDate to '2016-12-31'
-- Now you have 12 months and you can use below query to loop through each month starting from January
WHILE (#StartDate <= #EndDate)
BEGIN
DECLARE #Month INT = Month(#StartDate) -- At the begining #Month is equal to 1
-- Save #Month to temp table in each repeat
INSERT INTO #temp (mon)
SELECT #Month;
SET #StartDate = DATEADD(MONTH, 1, #StartDate); -- this line adds 1 value to #Month after first loop #Month will be 2
END