DECLARE @tb TABLE([a] varchar(10), [b] varchar(10))
INSERT INTO @tb
SELECT 'aa', '1111111'
UNION ALL SELECT 'bb', '66666666'
UNION ALL SELECT 'aa', '22222222'
UNION ALL SELECT 'aa', '333333333'
UNION ALL SELECT 'bb', '22222222'
SELECT A, COUNT(*) AS CT
FROM @TB
GROUP BY A
HAVING COUNT(*)>1 只選出有重復記錄
INSERT INTO @tb
SELECT 'aa', '1111111'
UNION ALL SELECT 'bb', '66666666'
UNION ALL SELECT 'aa', '22222222'
UNION ALL SELECT 'aa', '333333333'
UNION ALL SELECT 'bb', '22222222'