sql top 6 keywords to comma separated string

Hi I have an sql table like


productId        keyword        order
1                        keyword1      1
1                        keyword2      2
1                        keyword3      3
1                        keyword4      4
1                        keyword5      5
1                        keyword6      6

I want to do a inner join query to my products and want one column to be
"keyword1,keyword2,keyword3,keyword4,keyword5,keyword6"

if there are only 3 I don't want all the extra comma and ideally if keyword2 is missing just uses the next keyword etc.