Question

我正在尝试创建一个表：

CREATE TABLE [MyTable]
(
    [Id] [int] IDENTITY,
    [Column1] [int] NOT NULL,
    [Column2] [int] NOT NULL

    CONSTRAINT [PK_MyTable_Id] PRIMARY KEY ([Id])
    CONSTRAINT [UQ_MyTable_Column1_Column2] UNIQUE ([Column1], [Column2])
)

此脚本失败并显示错误：

已为列定义了PRIMARY KEY和UNIQUE约束 'Column2'，表'MyTable'。只允许一个。

为什么强制执行此限制？如何创建具有这些属性的表？我正在使用SQL Server 2008 R2。

Answer 1

您在主键约束后错过了逗号。

CREATE TABLE [MyTable]
(
    [Id] [int] IDENTITY,
    [Column1] [int] NOT NULL,
    [Column2] [int] NOT NULL

    CONSTRAINT [PK_MyTable_Id] PRIMARY KEY ([Id]),
    CONSTRAINT [UQ_MyTable_Column1_Column2] UNIQUE ([Column1], [Column2])
)

Answer 2

CREATE TABLE [MyTable]
(
    [Id] [int] IDENTITY,
    [Column1] [int] NOT NULL,
    [Column2] [int] NOT NULL

    CONSTRAINT [PK_MyTable_Id] PRIMARY KEY ([Id])

)

  ALTER TABLE [MyTable] ADD CONSTRAINT [UQ_MyTable_Column1_Column2] UNIQUE ([Column1], [Column2])

Answer 3

或者在主键声明和唯一约束声明之间加上逗号：

CREATE TABLE [MyTable]
(
    [Id] [int] IDENTITY,
    [Column1] [int] NOT NULL,
    [Column2] [int] NOT NULL

    CONSTRAINT [PK_MyTable_Id] PRIMARY KEY ([Id]),
    CONSTRAINT [UQ_MyTable_Column1_Column2] UNIQUE ([Column1], [Column2])
)

为什么我不能在同一个表上同时指定主键和唯一约束？

3 个答案: