SQL Server UNIQUE失效的有关问题_Sql Server

SQL Server UNIQUE失效的问题
CREATE TABLE dbo.Code_Index
(
code SMALLINT IDENTITY(1,1) CONSTRAINT PK_Code_Index_code PRIMARY KEY CLUSTERED (code ASC) WITH(PAD_INDEX=ON,FILLFACTOR=80,ALLOW_ROW_LOCKS=ON,ALLOW_PAGE_LOCKS=ON),

item VARCHAR(20) NOT NULL CONSTRAINT UQ_Code_Index_code UNIQUE NONCLUSTERED (code ASC) WITH(PAD_INDEX=ON,FILLFACTOR=80,ALLOW_ROW_LOCKS=ON,ALLOW_PAGE_LOCKS=ON)
)

以上命令建立的表格,依旧能够输入重复数据为什么?
注:输入重复数据是,提示提交数据错误,此数据为只读,表中依旧有两条记录.

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------解决方案--------------------
你写错了

CREATE TABLE dbo.Code_Index
(
code SMALLINT IDENTITY(1,1) CONSTRAINT PK_Code_Index_code PRIMARY KEY CLUSTERED (code ASC) WITH(PAD_INDEX=ON,FILLFACTOR=80,ALLOW_ROW_LOCKS=ON,ALLOW_PAGE_LOCKS=ON),

item VARCHAR(20) NOT NULL CONSTRAINT UQ_Code_Index_code UNIQUE NONCLUSTERED (item ASC) WITH(PAD_INDEX=ON,FILLFACTOR=80,ALLOW_ROW_LOCKS=ON,ALLOW_PAGE_LOCKS=ON)
)

INSERT INTO Code_Index(item)
VALUES ('a')

INSERT INTO Code_Index(item)
VALUES ('a')
SELECT * FROM Code_Index

------解决方案--------------------
CREATE TABLE dbo.Code_Index
(
code SMALLINT IDENTITY(1,1) CONSTRAINT PK_Code_Index_code PRIMARY KEY CLUSTERED (code ASC) WITH(PAD_INDEX=ON,FILLFACTOR=80,ALLOW_ROW_LOCKS=ON,ALLOW_PAGE_LOCKS=ON),

item VARCHAR(20) NOT NULL CONSTRAINT UQ_Code_Index_code UNIQUE NONCLUSTERED (code ASC) WITH(PAD_INDEX=ON,FILLFACTOR=80,ALLOW_ROW_LOCKS=ON,ALLOW_PAGE_LOCKS=ON)
)

红字部分如果你是用code，那么由于是自增，是不会重复的，应该改成item
------解决方案--------------------
try this,


CREATE TABLE dbo.Code_Index
(
code SMALLINT IDENTITY(1,1) CONSTRAINT PK_Code_Index_code PRIMARY KEY CLUSTERED (code ASC) 
WITH(PAD_INDEX=ON,FILLFACTOR=80,ALLOW_ROW_LOCKS=ON,ALLOW_PAGE_LOCKS=ON),

item VARCHAR(20) NOT NULL CONSTRAINT UQ_Code_Index_code UNIQUE NONCLUSTERED (item ASC) 
WITH(PAD_INDEX=ON,FILLFACTOR=80,ALLOW_ROW_LOCKS=ON,ALLOW_PAGE_LOCKS=ON)
)