How can I loop through all rows of a table? (MySQL)

Question

I have a table A and there is one primary key ID.

Now I want to go through all rows in A.

I found something like \'for each record in A\', but this seems to

Answer 1

Mr Purple's example I used in mysql trigger like that,

begin
DECLARE n INT DEFAULT 0;
DECLARE i INT DEFAULT 0;
Select COUNT(*) from user where deleted_at is null INTO n;
SET i=0;
WHILE i