创建索引视图来判断是否存在重复

USE tempdb
GO
IF OBJECT_ID('v_t') IS NOT NULL DROP VIEW v_t;
IF OBJECT_ID('t') IS NOT NULL DROP TABLE t;
GO
CREATE TABLE t(
id INT IDENTITY(1,1) PRIMARY KEY,
n NVARCHAR(20)
)
INSERT INTO t(n)
VALUES('a'),('a'),('b'),('b'),('b'),('c')
GO
CREATE VIEW dbo.v_t
WITH SCHEMABINDING
AS
SELECT n,COUNT_BIG(*) AS cnt
FROM dbo.t
GROUP BY n
GO
CREATE UNIQUE CLUSTERED INDEX ix_v_t ON dbo.v_t(n);
GO
SELECT * FROM v_t WHERE cnt>1
/*
n	cnt
a	2
b	3
*/