Is it possible to update an existing table in a single statement, using the output of a MERGE statement?

I know I can achieve this in many ways - this is a purely academic question to see if it's possible to do this in a single statement, in order to further my knowledge of SQL.

We're splitting an old, wide table into two narrower tables, a parent and a child:

create table WorkTable     ( ParentId     int             null     , ChildId      int         not null     , ParentField1 varchar(50) not null )create table ParentTable     ( Id     int         not null primary key identity     , Field1 varchar(50) not null )create table ChildTable     ( Id       int not null primary key identity     , ParentId int not null foreign key references ParentTable ( Id ) )

WorkTable contains a bunch of records from the original table - the ID from that table which we want to use as the ID in the child table (via identity_insert), and a field from that table that we actually want to set on the parent. For every row in WorkTable, therefore, we'll get 1 row in ParentTable and another in ChildTable.

Now I'm going to populate ParentTable, and also get the IDs of its newly-inserted records for the subsequent insert into ChildTable:

declare @IdsMap table      ( ParentId int not null      , ChildId  int not null )merge ParentTable dstusing (select ChildId     , ParentField1  from WorkTable) src on 1 = 0when not matched by target theninsert     ( Field1 )values     ( src.ParentField1 )output inserted.Id as [ParentId]     , src.ChildId -- can't do this with a standard INSERT...OUTPUT, hence the use of MERGE  into @IdsMap;update wkt   set wkt.ParentId = ids.ParentId   from WorkTable wkt           join       @IdsMap   ids on ids.ChildId = wkt.ChildId

This works, but it's ugly. I'd much prefer if I could simplify it into one statement, whereby the inserted IDs from ParentTable are updated directly back into Worktable - thus removing the need for the @IdsMap table var that exists solely to accomplish this update.

I thought I might be able to accomplish this by using the merge as nested DML:

update wkt   set wkt.ParentId = cte.ParentId  from WorkTable wkt           join(merge ParentTable dstusing (select ChildId     , ParentField1  from WorkTable) src on 1 = 0when not matched by target theninsert     ( Field1 )values     ( src.ParentField1 )output inserted.Id as [ParentId]     , src.ChildId) cte on cte.ChildId = wkt.ChildId

but MSSQL says no:

A nested INSERT, UPDATE, DELETE, or MERGE statement is notallowed on either side of a JOIN or APPLY operator.

Nested DML inside a CTE similarly fails:

;with cte as(select *  from(merge ParentTable dstusing (select ChildId     , ParentField1  from WorkTable) src on 1 = 0when not matched by target theninsert     ( Field1 )values     ( src.ParentField1 )output inserted.Id as [ParentId]     , src.ChildId) _)update wkt   set wkt.ParentId = cte.ParentId  from WorkTable wkt           join                 cte on cte.ChildId = wkt.ChildId

A nested INSERT, UPDATE, DELETE, or MERGE statement is not allowed in a SELECTstatement that is not the immediate source of rows for an INSERT statement.

Is there any way to achieve what I'm looking for?