I have a file with product id's in column A, and Category ID's in column B. Rows with a blank column B that have an entry in column C i've added to the sheet and sorted by column A so I can see which products have new categories that I have to add to. How can I combine matching matching cells/rows using column A so that the category ID's are all on the same row so I can just do =(B1&C1) in another column to combine the category IDs

1397 85
1397 ,482
1398 85
1398 ,482

Thank you in advance
Pete