How can I use ForAll and RemoveIf to remove items in one collection that are missing in another?

[pwrappr01]

I have two collections I want to compare so I can ensure they match exactly. Here are samples of the two collections:

Collection1

ID	Item
3	C

Collection2

ID	Item
1	A
2	B
3	C

How can I write my ForAll( RemoveIf ) so it removes IDs 1 and 2 from Collection2 because they are missing from Collection1?

[Rebetcha]

Hi @pwrappr01 ,

I dont't think you need the ForAll in this case. The RemoveIf already allows you to loop through a table.

Why not do?: 

RemoveIf(Collection2, Not(ID in Collection1.ID))

[pontusofsweden]

Hi @pwrappr01 !

You dont need to use ForAll since RemoveIf loops through all lines anyway. Try this formula:

RemoveIf(
    Collection2,
    CountRows(
        Filter(
            Collection1,
            Id = Collection2[@Id] && Item = Collection2[@Item]
        )
    ) < 1
)

BR

Pontus