Code error in a SQL Server While-If Loop - sql

Question

I know that there are other posts with code that solve my problem but I don't want to take another's code so I'm trying to do it by myself and I'm stuck with the month not increasing problem, so if anyone can help me with that mistake it will be awesome.
The problem is:
I have to populate the table Time from year 1990 to 2016 with all the months and days, I have already achieved that the code works and it populates correctly the years and the days but months increases to January (1) and then is not increasing so the table is filled with all months being January (LOL)
Here's my code:
create table Time
(
Year int,
Month int,
Day int
)
create procedure pTime
as
declare #year int, #month int, #day int;
set #year = 1990;
set #month = 12;
set #day = 10;
while(#year<=2016)
Begin
If(#day = 29)
Begin
set #month = #month + 1;
If(#month = 13)
Begin
set #month = 1;
set #day = 1;
set #year = #year + 1;
insert into Time values (#year, #month, #day);
End
End
else
Begin
If(#day = 29)
Begin
set #month = #month + 1;
set #day = 1;
insert into Time values (#year, #month, #day);
End
Else
Begin
insert into Time values (#year, #month, #day);
set #day = #day + 1;
End
End
End
Any idea where is my mistake or any suggestion?

Answer 1

I didn't look very closely for your mistake because SQL Server has some helpful date arithmetic functions. Here's simplified version of your stored procedure:
create procedure pTime
as
declare #theDate date = '12/10/1990', #days int = 0
while #theDate < '1/1/2016'
begin
insert into Time (Year, Month, Day) values (datepart(year, #theDate), datepart(month, #theDate), datepart(day, #theDate));
set #theDate = dateadd(day, 1, #theDate)
end

Answer 2

Another faster approach would be to use a tally table. Note the code below:
WITH
E(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),
iTally(N) AS (SELECT ROW_NUMBER() OVER (ORDER BY (SELECT 1))-1 FROM E a,E b,E c,E d,E e),
dates(dt) AS
(
SELECT TOP(datediff(DAY,'19900101','20160101')) DATEADD(day,N,'19900101')
FROM iTally
)
--INSERT [time] --uncomment for the insert, leave commented to see what will be inserted
SELECT YEAR(dt), MONTH(dt), DAY(dt)
FROM dates;

Answer 3

Why do you need If(#year = 29) condition? In your code this block never will be executed. try this:
create procedure pTime
as
declare #year int, #month int, #day int;
set #year = 1990;
set #month = 12;
set #day = 10;
while(#year<=2016)
Begin
If(#day = 29)
Begin
set #month = #month + 1;
set #day = 1;
If(#month = 13)
Begin
set #month = 1;
set #year = #year + 1;
insert into Time values (#year, #month, #day);
End
End
else
Begin
If(#day = 29)
Begin
set #month = #month + 1;
set #day = 1;
insert into Time values (#year, #month, #day);
End
Else
Begin
insert into Time values (#year, #month, #day);
set #day = #day + 1;
End
End
End
I think first assignment set #day = 1; wasn't in right place. After increasing #month value you should set also #day to 1;