Question

当我运行底部看到的SQL时，为什么会返回：

Msg 1776，Level 16，State 0，Line 2
  引用表'pricedex.table_a'中没有主键或候选键与外键'FK_delete_from_parent'中的引用列列表匹配。

Msg 1750，Level 16，State 0，Line 2
  无法创建约束。查看以前的错误。

代码：

SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

SET ANSI_PADDING ON
GO

CREATE TABLE table_a 
(
    [column_1] [int] NULL,
    [column_2] [int] NULL
)

CREATE TABLE table_b 
(
    [column_1] [int] NULL,
    [column_2] [int] NULL
)

GO

CREATE NONCLUSTERED INDEX IX_app ON table_a (column_1, column_2)
GO

CREATE NONCLUSTERED INDEX IX_app ON table_b (column_1, column_2)
GO

SET ANSI_PADDING OFF
GO

ALTER TABLE table_b WITH CHECK
ADD CONSTRAINT FK_delete_from_parent 
    FOREIGN KEY (column_1, column_2) REFERENCES table_a (column_1, column_2) 
       ON DELETE CASCADE
GO

Answer 1

您需要将PRIMARY KEY添加到table_a并将PK列更改为NOT NULL：

CREATE TABLE table_a (
    [column_1] [int] NOT NULL,
    [column_2] [int] NOT NULL,
    PRIMARY KEY(column_1, column_2)            -- compound primary key
);

CREATE TABLE table_b (
    [column_pk] [int] NOT NULL PRIMARY KEY,    -- you probably want different pk
    [column_1] [int] NULL,
    [column_2] [int] NULL
);

-- adding foreign key constraint
ALTER TABLE table_b WITH CHECK
ADD CONSTRAINT FK_delete_from_parent FOREIGN KEY (column_1, column_2)
REFERENCES table_a (column_1, column_2) ON DELETE CASCADE;

的 SqlFiddleDemo

修改

Create Foreign Key Relationships：

外键约束不必仅链接到主键另一个表中的键约束;它也可以定义为参考另一个表中 UNIQUE约束的列。

CREATE TABLE table_a ( [column_1] [int] NOT NULL, -- with UNIQUE column can be nullable [column_2] [int] NOT NULL, UNIQUE(column_1, column_2) -- anyway this table should have PK );

的 SqlFiddleDemo2

请注意，如果列可以为空并且您有NULL个值ON DELETE CASCADE，则不会从相应的表中删除记录。

如何使用复合键在SQL Server中执行参照完整性？

1 个答案: