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

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 be not how you do it in MySQL.

Thing is for each row I want to take a field and transform it, insert it into another table and then update some of the row's fields. I can put the select part and the insert into one statement, but I don't know how to get the update in there as well. So I want to loop. And for practice I don't want to use anything else than MySQL.

edit

I would appreciate an example.

And a solution which does not need to be put into a procedure.

edit 2

okay think of this scenario:

Table A and B, each with fields ID and VAL.

Now this is the pseudo code for what I want to do:

for(each row in A as rowA)
{
  insert into B(ID, VAL) values(rowA[ID], rowA[VAL]);
}

basically copying content of A into B using a loop.

(this is just a simplified example, of course you wouldn't use a loop for this.) }

CURSORS are an option here, but generally frowned upon as they often do not make best use of the query engine. Consider investigating 'SET Based Queries' to see if you can achieve what it is you want to do without using a CURSOR.

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<n DO 
  INSERT INTO user_notification(notification_id,status,userId)values(new.notification_id,1,(Select userId FROM user LIMIT i,1)) ;
  SET i = i + 1;
END WHILE;
end

You should really use a set based solution involving two queries (basic insert):

INSERT INTO TableB (Id2Column, Column33, Column44)
SELECT id, column1, column2 FROM TableA

UPDATE TableA SET column1 = column2 * column3

And for your transform:

INSERT INTO TableB (Id2Column, Column33, Column44)
SELECT 
    id, 
    column1 * column4 * 100, 
    (column2 / column12) 
FROM TableA

UPDATE TableA SET column1 = column2 * column3

Now if your transform is more complicated than that and involved multiple tables, post another question with the details.

    Use this:

    $stmt = $user->runQuery("SELECT * FROM tbl WHERE ID=:id");
    $stmt->bindparam(":id",$id);
    $stmt->execute();

        $stmt->bindColumn("a_b",$xx);
        $stmt->bindColumn("c_d",$yy);


    while($rows = $stmt->fetch(PDO::FETCH_BOUND))
    {
        //---insert into new tble
    }