I have this sticky situation where I have a table with a parent/child relationship in which I have to match the child field information to match the parent.

DocID AttachID ProdField
1.94.2560 1 abc123
1.94.2561 1 Null
1.94.2567 6 def456
1.94.2568 6 Null
1.94.2569 6 Null
1.94.2570 6 Null
1.94.2571 6 Null


What I would like to do is to use the AttachID to recursively go down the column and update the Prodfield according to the first distinct AttachID. The output would look like this

DocID AttachID ProdField
1.94.2560 1 abc123
1.94.2561 1 abc123
1.94.2567 6 def456
1.94.2568 6 def456
1.94.2569 6 def456
1.94.2570 6 def456
1.94.2571 6 def456


My thought process is that I would have to use a combination of CTE and update or maybe a CASE statement to make this work. However, at this moment, I am just spinning my wheels and I figured some fresh eyes probably could point me in the right direction.