wrong syntax to use near 'declare exists_check int' - mysql

Question

I'm writing an script to update a db schema, the script is the following:
delimiter //
begin
set #check_exists = 0;
select count(*)
into #check_exists
from information_schema.columns
where table_schema = 'my_app'
and table_name = 'users'
and column_name = 'points';
if (#check_exists = 0) then
alter table my_app.users
add points int not null default 0
end if;
end //
delimiter
when I run it, i get the below error:
Reason:
SQL Error [1064] [42000]: (conn=34) You have an error in your SQL syntax;
check the manual that corresponds to your MariaDB server version for the right syntax
to use near 'set #check_exists = 0;
I have already checked the answers the below two posts but none solves my problem.
this question where the solution was to change the delimiter, and to
this question where the solution was to remove the DECLARE keyword and just declare the variable as it is in the MariaDB manual here with set #var int;

Answer 1

I think you need to have a CREATE PROCEDURE before your BEGIN statement. So:
delimiter //
CREATE PROCEDURE UPDATE_SCHEMA()
begin
set #check_exists = 0;
(...your other script here...)
end//
delimiter ;
call UPDATE_SCHEMA();
An additional note: check_exists in your if statement needs a #

Answer 2

According to the BEGIN END documentation here, the syntax is:
BEGIN [NOT ATOMIC]
[statement_list]
END [end_label]
And here is what I did not know:
NOT ATOMIC is required when used outside of a stored procedure. Inside stored procedures or within an anonymous block, BEGIN alone starts a new anonymous block.
As I'm not using the BEGIN END in a stored procedure, I have to add the NOT ATOMIC after the BEGIN keyword.
So the code should look like this:
delimiter //
begin not atomic
set #check_exists = 0;
-- rest of the code here...