Creating a temporary table within a TRIGGER with GROUP BY - sql-server

Question

I need to create and use a temporary table with GROUP BY clause within a trigger, but I'm having difficulties doing so.
My attempt:
Here I'm trying to use two temporary tables which are dropped after the trigger reach an end.
First I create a #Temptable and the trigger.
CREATE TABLE #TempTable (admID smallint, diagID smallint);
CREATE TRIGGER tr_newTest
ON Adm_Diag
FOR INSERT
AS
BEGIN
...
END
Since the table inserted only contains rows for a current INSERT and UPDATE statements I'm passing several INSERT and UPDATE statements to #TempTable.
DECLARE #admID smallint
SELECT #admID = Adm_ID
FROM inserted
DECLARE #diagID smallint
SELECT #diagID=Diag_ID
FROM inserted
INSERT INTO #TempTable VALUES (#admID, #diagID)
Now with this data I want to create a temporary table that groups the rows of #TempTable:
SELECT *
INTO #TempGroupTable
FROM
(
SELECT admID, COUNT(*) as Diag
FROM #TempTable
GROUP BY admID
) t1
WHERE Diag > 2
The whole script
CREATE TABLE #TempTable (admID smallint, diagID smallint);
CREATE TRIGGER tr_newTest
ON Adm_Diag
FOR INSERT
AS
BEGIN
DECLARE #admID smallint
SELECT #admID = Adm_ID
FROM inserted
DECLARE #diagID smallint
SELECT #diagID=Diag_ID
FROM inserted
INSERT INTO #TempTable VALUES (#admID, #diagID)
-- Below I'm tring to create #TempGroupTable
SELECT *
INTO #TempGroupTable
FROM
(
SELECT admID, COUNT(*) as Diag
FROM #TempTable
GROUP BY admID
) t1
WHERE Diag > 2
END
After executing the trigger I get an error:
Msg 208, Level 16, State 0, Line 41 Invalid object name
'#TempGroupTable'.
How can I create #TempGroupTable?

Answer 1

Not quote sure what you are trying to do but would a global temporary tables which starts with ## work for you? So make the #TempGroupTable into ##TempGroupTable?

Answer 2

Why not dispense with all the overhead of temp tables and variables? Try:
CREATE TRIGGER tr_newTest
ON Adm_Diag
INSTEAD OF INSERT
AS
BEGIN
INSERT INTO Adm_Diag (adminID, Diag)
SELECT admID, COUNT(*) as Diag
FROM inserted
GROUP BY admID
END