Sql Server 2008 MERGE - best way to get counts

You could specify an OUTPUT clause on your MERGE statement and get an output report of what's been done during MERGE.

MERGE (targetTable) AS t 
USING (sourceTable) AS s
ON t.ID = s.ID
WHEN MATCHED THEN
  (some statements)
WHEN NOT MATCHED THEN
  (some statements)
OUTPUT
  $action, inserted.ID 'inserted', deleted.ID 'deleted'
;

This will give you a row for each "action" (insert, update, delete) for each operation. If it's a lot of statements, you could also OUTPUT INTO @tableVar and then look at the table variable.

DECLARE @tableVar TABLE (MergeAction VARCHAR(20), InsertedID INT, DeletedID INT)

MERGE (targetTable) AS t 
USING (sourceTable) AS s
ON t.ID = s.ID
WHEN MATCHED THEN
      (some statements)
WHEN NOT MATCHED THEN
      (some statements)
OUTPUT
      $action, inserted.ID 'inserted', deleted.ID 'deleted' INTO @tableVar
;

SELECT MergeAction, COUNT(*) 
FROM @tableVar  
GROUP BY MergeAction

Check out the Books Online for details on the MERGE statement and the OUTPUT clause.

Marc

To extract into individual vars, can post process answer by marc_s using pivot:

    declare
        @mergeResultsTable table (MergeAction VARCHAR(20));

    declare
        @insertCount int,
        @updateCount int,
        @deleteCount int;

    merge ...
    output $action into @mergeResultsTable; 

    select @insertCount = [INSERT],
           @updateCount = [UPDATE],
           @deleteCount = [DELETE]
      from (select 'NOOP' MergeAction -- row for null merge into null
             union all
            select * from @mergeResultsTable) mergeResultsPlusEmptyRow     
     pivot (count(MergeAction) 
       for MergeAction in ([INSERT],[UPDATE],[DELETE])) 
        as mergeResultsPivot;

The union 'noop' row can be removed if init vars to 0 or know that source or target table has >0 rows.