how to fnd a duplicate values from a column

DECLARE @t TABLE (stid  INT, stname VARCHAR(10))
INSERT INTO @t(stid, stname) VALUES (1, '1')
INSERT INTO @t(stid, stname) VALUES (2, '1')
INSERT INTO @t(stid, stname) VALUES (3, '2')
INSERT INTO @t(stid, stname) VALUES (4, '3')
INSERT INTO @t(stid, stname) VALUES (5, '4')
INSERT INTO @t(stid, stname) VALUES (6, '5')
INSERT INTO @t(stid, stname) VALUES (7, '6')


select * from @t where stname IN ( SELECT stname FROM @t GROUP BY stname HAVING COUNT(stname) > 1)