我如何知道 CONSTRAINT_NAME 是主键还是外键？

Question

在 SQL Server 2005 上使用此 SQL，

SELECT CONSTRAINT_NAME
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
WHERE TABLE_NAME = @TableName
  AND COLUMN_NAME=@ColumnName

我得到主键和外键。

如何只获取外键？ 如何查看约束是主键还是外键？

谢谢

Answer 1

找到了一个更优雅的解决方案 此处

为了完整性起见，在下面添加了代码，但所有功劳都归功于 Pinal Dave

SELECT f.name AS ForeignKey,
   OBJECT_NAME(f.parent_object_id) AS TableName,
   COL_NAME(fc.parent_object_id, 
   fc.parent_column_id) AS ColumnName,
   OBJECT_NAME (f.referenced_object_id) AS ReferenceTableName,
   COL_NAME(fc.referenced_object_id, 
   fc.referenced_column_id) AS ReferenceColumnName
FROM sys.foreign_keys AS f
LEFT JOIN sys.foreign_key_columns AS fc
   ON f.OBJECT_ID = fc.constraint_object_id

如果您只想要主键...

SELECT i.name AS IndexName,
        OBJECT_NAME(ic.OBJECT_ID) AS TableName,
        COL_NAME(ic.OBJECT_ID,ic.column_id) AS ColumnName
FROM sys.indexes AS i
        INNER JOIN sys.index_columns AS ic
        ON i.OBJECT_ID = ic.OBJECT_ID 
    AND i.index_id = ic.index_id
WHERE i.is_primary_key = 1

将此添加为附加答案，因为它与我的上一个答案相去甚远:)

Answer 2

我在 SQL Server 2005 中使用以下 SQL 来按主键获取约束名称：

SELECT Constraint_Name 
FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS 
WHERE UNIQUE_CONSTRAINT_NAME = 
   (SELECT CONSTRAINT_NAME 
    FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
    WHERE TABLE_NAME = @TableName AND COLUMN_NAME = @ColumnName)

按外键获取约束名称：

SELECT CONSTRAINT_NAME 
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
WHERE TABLE_NAME = @TableName AND COLUMN_NAME = @ColumnName

按约束名称获取外键的表和字段：

SELECT TABLE_NAME, COLUMN_NAME 
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
WHERE CONSTRAINT_NAME = @ConstraintName

按约束名称获取主键的表和字段:

SELECT TABLE_NAME, COLUMN_NAME 
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
WHERE CONSTRAINT_NAME = 
    (SELECT UNIQUE_CONSTRAINT_NAME 
     FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS 
     WHERE CONSTRAINT_NAME = @ConstraintName)

Answer 3

这取决于您的 DBMS，但约束应该在某处具有目标表和列。

如果是外键约束，则目标表将与当前表不同。 尝试

select *

查看

select constraint_name

您可以使用的所有神奇列。

Answer 4

SELECT CONSTRAINT_NAME
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE
WHERE TABLE_NAME = @TableName
  AND COLUMN_NAME=@ColumnName
  AND REFERENCED_COLUMN_NAME IS NOT NULL

Answer 5

这不是最优雅的解决方案，但 MS SQL Server 使用 PK & 键的 FK 前缀命名约定，以便您可以使用类似的内容...

SELECT CONSTRAINT_NAME 
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
WHERE TABLE_NAME = @TableName
AND LEFT(CONSTRAINT_NAME,2) = 'FK'

如果那是您的 DBMS :)

编辑

当我尝试 Quassnoi 的答案时，我得到了“无效的列名称 'REFERENCED_COLUMN_NAME'”。 错误。

Answer 6

我用类似的东西。 它也适用于 SQL Server 2000。

select  object_name(fkx.constid) as fk_name,
        fkx.keyno as num,
        object_name(fkx.fkeyid) as child_table,
        col_name(fkx.fkeyid, fkx.fkey) as child_column,
        object_name(fkx.rkeyid) as parent_table,
        col_name(fkx.rkeyid, fkx.rkey) as parent_column
from sysforeignkeys fkx
order by fk_name, fkx.keyno

这一切都在系统表和视图中，并且有很好的记录。