Question

我的最终目标是实现以下目标：

CREATE FOREIGN KEY IF NOT EXISTS FOREIGN KEY

由于该陈述似乎并不存在，我试图将它整合起来。

我有一个声明，如果它存在，将返回FK名称：

SELECT f.name AS ForeignKey
FROM sys.foreign_keys AS f 
WHERE OBJECT_NAME(f.parent_object_id) = 'myTableName'

我有一个声明添加了所需的外键：

ALTER TABLE myTableName
WITH CHECK 
ADD CONSTRAINT [FK_myTableName_otherTable] 
FOREIGN KEY([columnName]) 
REFERENCES otherTable ([otherColumn])

我不能，为了我的生活，弄清楚如何将它们混合成一个单独的陈述。

绝对要求该解决方案在MS SQL 2000和MS SQL 2005中均有效。

Answer 1

if not exists (SELECT f.name AS ForeignKey
FROM sys.foreign_keys AS f 
WHERE OBJECT_NAME(f.parent_object_id) = 'myTableName'
)
begin
    ALTER TABLE myTableName
    WITH CHECK 
    ADD CONSTRAINT [FK_myTableName_otherTable] 
    FOREIGN KEY([columnName]) 
    REFERENCES otherTable ([otherColumn])
end

Answer 2

SQL Server 2005中引入了

sys.foreign_keys。您必须使用sysobjects兼容SQL Server 2000和SQL Server 2000。 2005。

试试这个SQL：

IF NOT EXISTS (
    SELECT NULL FROM sysobjects 
    WHERE name = 'FK_myTableName_otherTable' 
    AND parent_obj = OBJECT_ID(N'myTableName'))
ALTER TABLE myTableName
WITH CHECK 
ADD CONSTRAINT [FK_myTableName_otherTable] 
FOREIGN KEY([columnName]) 
REFERENCES otherTable ([otherColumn])

Answer 3

if not exists (
    SELECT f.name AS ForeignKey
    FROM sys.foreign_keys AS f 
    WHERE OBJECT_NAME(f.parent_object_id) = 'myTableName') 
begin
    ALTER TABLE myTableName
    WITH CHECK 
    ADD CONSTRAINT [FK_myTableName_otherTable] 
    FOREIGN KEY([columnName]) 
    REFERENCES otherTable ([otherColumn])
end

如何以兼容MSSQL 2000和2005的方式将这两个SQL语句合并为一个？

3 个答案: