Stored procedure in Microsoft SQL Server conversion before inserting - sql

Question

I am trying to create a stored procedure that does manipulation of parameter passed in before inserting it into my table. One of the columns in my table is called DATE_CHANGED and basically what I gg to do here is to change a passed date parameter like December 1st 2017 to 20171201. This is an int value.
I wrote a stored procedure like this:
CREATE PROCEDURE date_generate
#startDate DATE
AS
BEGIN
DECLARE #DATE_KEY INT
#DATE_KEY = CONVERT(INT, FORMAT(#startDate, 'YYYYMMDD')
INSERT INTO table date_key = #DATE_KEY
END
However I get an error
Incorrect syntax near '#DATE_KEY
Are local variable declared only used for SQL query statement like
select *
from table
where date_key = #DATE_Key?

Answer 1

There is more than one error.
Use SET to assign values to a variable.
Have a look at INSERT statement too.
CREATE PROCEDURE date_generate
#startDate date
AS
BEGIN
DECLARE #DATE_KEY int;
SET #DATE_KEY = CONVERT(int, format(#startDate, 'YYYYMMDD'));
INSERT INTO DATE_CHANGED (date_key)
VALUES (#DATE_KEY);
END

Answer 2

This seems really strange. You don't even need a local variable. Based on your code, you could write:
create procedure date_generate (
#startDate date
) as
begin
insert into table (date_key)
values ( convert(int, format(#startDate, 'YYYYMMDD')) );
end; -- date_generate
Or, I might write:
create procedure date_generate (
#startDate date
) as
begin
insert into table (date_key)
values ( year(#startDate) * 10000 + month(#startDate) * 100 + day(#startDate) );
end;
Why you would have a table with a single date on each row doesn't really make sense to me. Why you would be storing that "date" as an integer also doesn't make sense.

Answer 3

As far as I've understood, your stored procedure accepts a DATE as a parameter, but you need to do an INSERT with an INT.
You can easily convert a DATE to a VARCHAR and then to a INT, this way:
DECLARE #DateASInt INT = CAST(CONVERT(VARCHAR(8), #startDate, 112) AS INT);
So, your stored procedure will be like this:
CREATE PROCEDURE date_generate
#startDate date
AS
BEGIN
INSERT INTO date_key
VALUES (CAST(CONVERT(VARCHAR(8), #startDate, 112) AS INT));
END