如何使用Information_Schema在SQL Server中查找外键引用？

使用 SQL Server 的信息架构获取外键引用

在 SQL Server 中，识别外键引用的表和列可能是有价值的信息用于理解数据关系。要获取此信息，我们可以利用 information_schema 视图。

SELECT 
     KCU1.CONSTRAINT_SCHEMA AS FK_CONSTRAINT_SCHEMA 
    ,KCU1.CONSTRAINT_NAME AS FK_CONSTRAINT_NAME 
    ,KCU1.TABLE_SCHEMA AS FK_TABLE_SCHEMA 
    ,KCU1.TABLE_NAME AS FK_TABLE_NAME 
    ,KCU1.COLUMN_NAME AS FK_COLUMN_NAME 
    ,KCU1.ORDINAL_POSITION AS FK_ORDINAL_POSITION 
    ,KCU2.CONSTRAINT_SCHEMA AS REFERENCED_CONSTRAINT_SCHEMA 
    ,KCU2.CONSTRAINT_NAME AS REFERENCED_CONSTRAINT_NAME 
    ,KCU2.TABLE_SCHEMA AS REFERENCED_TABLE_SCHEMA 
    ,KCU2.TABLE_NAME AS REFERENCED_TABLE_NAME 
    ,KCU2.COLUMN_NAME AS REFERENCED_COLUMN_NAME 
    ,KCU2.ORDINAL_POSITION AS REFERENCED_ORDINAL_POSITION 
FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS AS RC 

INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS KCU1 
    ON KCU1.CONSTRAINT_CATALOG = RC.CONSTRAINT_CATALOG  
    AND KCU1.CONSTRAINT_SCHEMA = RC.CONSTRAINT_SCHEMA 
    AND KCU1.CONSTRAINT_NAME = RC.CONSTRAINT_NAME 

INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS KCU2 
    ON KCU2.CONSTRAINT_CATALOG = RC.UNIQUE_CONSTRAINT_CATALOG  
    AND KCU2.CONSTRAINT_SCHEMA = RC.UNIQUE_CONSTRAINT_SCHEMA 
    AND KCU2.CONSTRAINT_NAME = RC.UNIQUE_CONSTRAINT_NAME 
    AND KCU2.ORDINAL_POSITION = KCU1.ORDINAL_POSITION 

示例：

假设我们有表 T_ALV_Ref_FilterDisplay 和 T_AP_Ref_Customer，并且 T_ALV_Ref_FilterDisplay 有外键约束参考T_AP_Ref_Customer.MDT_ID。要查找引用的表和列，我们可以执行查询：

SELECT 
    REFERENCED_TABLE_SCHEMA, 
    REFERENCED_TABLE_NAME, 
    REFERENCED_COLUMN_NAME 
FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS 
WHERE 
    FK_TABLE_SCHEMA = 'dbo' 
    AND FK_TABLE_NAME = 'T_ALV_Ref_FilterDisplay' 
    AND FK_COLUMN_NAME = 'FA_MDT_ID';

这将返回以下结果：

REFERENCED_TABLE_SCHEMA | REFERENCED_TABLE_NAME | REFERENCED_COLUMN_NAME
------------------------ | ---------------------- | ----------------------
dbo                      | T_AP_Ref_Customer      | MDT_ID

限制：

请注意，information_schema 不包含有关索引的信息。如果外键引用基于唯一索引，则需要使用 Microsoft 专有表。

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