Using 3 tables in Merge function T-SQL

Question

Hi there,
I have a source table A and one View ,Target table B
I was trying to write Merge function for incremental load I mean it is type1 load
Table A should look at View   if it doesn't find the record then load into table B (Target)
the columns are ID and Type
if ID is same and type name is different then should update type in the Table B (Target)
I usually write merge function like below 
Merge table x
using table y
on x.id=y.id
when matched  then
update set x.description=y.description
when not matched then
insert (id,description)
values(id,description)
but I don't understand how to write in my scenario. can anyone guide me please.

Answer 1

Please try this.
Declare @MergeData Table
Col1 Int,
Col2 Varchar(10),
ActionDone Varchar(10)
Select * Into #Temp_SourceA From SourceA
Insert @MergeData
Select Col1,Col2,ActionDone
From
Merge #Temp_SourceA As Trgt
Using View_Source As Src
On Trgt.Col1 = Src.Col1
When Matched And
Trgt.Col2 <> Src.Col2
Then Update Set Trgt.Col2 = Src.Col2
When Not Matched Then
Insert (Col1,Col2)
Values (Src.Col1,Src.Col2)
Output $action ActionDone,Inserted.Col1,Inserted.Col2
)Data
Select * From @MergeData
Insert Into TargetA
Select Col1,Col2 From @MergeData Where ActionDone = 'INSERT'
Update T1
Set Col2 = T2.Col2
From TargetA T1
Inner Join @MergeData T2 On T1.Col1 = T2.Col1 And T2.ActionDone = 'Update'
Drop Table #Temp_SourceA
--Select * From View_Source
--Select * From SourceA
Please have look on the comment