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

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.