How to Find Foreign Key References in SQL Server Using Information_Schema?

Getting Foreign Key References with SQL Server's Information Schema

In SQL Server, identifying the table and column a foreign key references can be valuable information for understanding data relationships. To obtain this information, we can leverage the information_schema views.

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 

Example:

Suppose we have tables T_ALV_Ref_FilterDisplay and T_AP_Ref_Customer, and T_ALV_Ref_FilterDisplay has a foreign key constraint referencing T_AP_Ref_Customer.MDT_ID. To find the referenced table and column, we can execute the query:

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';

This would return the following result:

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

Limitations:

Note that the information_schema doesn't include information about indices. If the foreign key reference is based on a unique index, you'll need to use Microsoft proprietary tables instead.

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