Question

I would like to duplicate every row in my table, but in the duplicate row the value of one column will need to overwrite an existing value in another column (an intermediary step in normalising my tables).

So what I need is something like

INSERT INTO `performers` SELECT * FROM `performers` 
SET `performers`.`piano` = `performers`.`singing`

As I’m no good at SQL the above, as expected, didn’t work. Any ideas?

Answer 1

If only the duplicate row needs to have this values changed, then you can modify your INSERT:

INSERT INTO `performers`(col1, col2, col3, piano, singing)
SELECT col1, col2, col3, singing, singing
FROM `performers`