How to convert a query from SQL to be inserted in the condition of a Case in Web Designer?

In One Identity Manager 8.2 I would like to edit the (viewing) condition of a Case inside a Switch in the Web Designer:

The problem is that I don't know how to convert the query from SQL to the language supported by the condition. The docs says it's WebSQL, but my attempt in WebSQL still doesn't work.

The query in the following:

exists(select *
from Person
Where UID_Person = '[here I would like to insert the value of GetUser()]'
And (
    IsExternal = 0 Or
        (IsExternal = 1
        And UID_Person IN (
            select UID_Person from PersonInAERole Where UID_AERole = '[a known UID]'
            )
        )
    )
)

What I've tried:

format("exists(select *
from Person
Where UID_Person = '{0}'
And (
    IsExternal = 0 Or
        (IsExternal = 1
        And UID_Person IN (
            select UID_Person from PersonInAERole Where UID_AERole = '[a known UID]'
            )
        )
    )
)", GetUser())

How should I write it?