[woocommerce 2.4.10] – change variable product in bulk

Hi – I’ve got 100+ products, all with the same variables (sizes A and B)

Right now size A is the default for all these products, but I wan’t to change that to B for alle products. Is there any plugins, or easy tools to do this ? I got access to phpmyadmin if there is some sql query that could fix it easy.

Also all my products have random SKU no. Some has the same cause i duplicate and change the info for each product, and sometimes forget to change the SKU… is there any plugin that will automaticly make the SKU in a pattern I choose?

I’d like all my products to have e.g PL001, PL002 etc.