Make a backup of your database ...
Did you make a really good backup of your database? :lookaroun
NOTE: If you forget to make a backup of your database or really make a mess ... this should hopefully not be hard to fix if things go wrong ...
1 Create a New Category that you will be using to place ALL products in this New Category on Sale
2 Check to see what the new categories_id is for that category
Let's assume the new categories_id is 1155 ...
To get ALL Products that were added prior to January 1, 2014 to be in this new category that is categories_id 1155, you can run this SQL command:
insert into products_to_categories (products_id, categories_id) select products_id, 1155
from products
where products_date_added < '2014-01-01 00:00:00'
and products_id not in (select products_id from products_to_categories where categories_id = 1155);
So now all Products created before January 1, 2014 are in categories_id 1155 ...
However, we need to now get all of those Products to use this new categories_id 1155 to be their master_categories_id ...
Remember, to make this change will cancel any current SaleMaker sale prices on these Products ...
Use the SQL command:
UPDATE products SET master_categories_id = 1155 WHERE products_date_added < '2014-01-01 00:00:00';
Now, all of these Products added before January 1, 2014 are using the master_categories_id 1155 ...
Next, you need to add a SaleMaker sale on this category ...
Read through this slowly and think about what this is doing and if this is what you are trying to accomplish ...
If so, great, you are good to go ... if you have questions, ask them before you try this ...