计算临时表返回的记录数 - SQL Server

My script is as below

我的脚本如下

CREATE TABLE #t (Id int, Name varchar(10))
INSERT INTO #t VALUES (1, 'A')
INSERT INTO #t VALUES (1, 'B')
INSERT INTO #t VALUES (1, 'C')
INSERT INTO #t VALUES (1, 'D')
INSERT INTO #t VALUES (2, 'E')

SELECT COUNT(0)FROM (SELECT COUNT(0) FROM #t GROUP BY Id) a
CREATE TABLE #