Inserisci N valori casuali nella tabella

Nessun loop, un inserto

;WITH cte AS
(  --there are easier ways to build a numbers table
   SELECT
       ROW_NUMBER() OVER (ORDER BY (select 0)) AS rn
   FROM
      sys.columns c1 CROSS JOIN sys.columns c2 CROSS JOIN sys.columns c3
)
INSERT INTO [T1] ([Value])
OUTPUT INSERTED.ID INTO T2  -- direct insert to T2
SELECT RAND(CHECKSUM(NEWID()))
FROM cte
WHERE rn <= @N;