How can I list all foreign keys referencing a given table in SQL Server?

Question

I need to remove a highly referenced table in a SQL Server database. How can I get a list of all the foreign key constraints I will need to remove in order to drop the tabl

Answer 1

You can find through below query :

 SELECT OBJECT_NAME (FK.referenced_object_id) 'Referenced Table', 
      OBJECT_NAME(FK.parent_object_id) 'Referring Table', FK.name 'Foreign Key', 
      COL_NAME(FK.referenced_object_id, FKC.referenced_column_id) 'Referenced Column',
      COL_NAME(FK.parent_object_id,FKC.parent_column_id) 'Referring Column'
     FROM sys.foreign_keys AS FK
             INNER JOIN sys.foreign_key_columns AS FKC 
                 ON FKC.constraint_object_id = FK.OBJECT_ID
     WHERE OBJECT_NAME (FK.referenced_object_id) = 'YourTableName'
     AND COL_NAME(FK.referenced_object_id, FKC.referenced_column_id) = 'YourColumnName'
     order by  OBJECT_NAME(FK.parent_object_id)

Answer 2

Not sure why no one suggested but I use sp_fkeys to query foreign keys for a given table:

EXEC sp_fkeys 'TableName'

You can also specify the schema:

EXEC sp_fkeys @pktable_name = 'TableName', @pktable_owner = 'dbo'

Without specifying the schema, the docs state the following:

If pktable_owner is not specified, the default table visibility rules of the underlying DBMS apply.

In SQL Server, if the current user owns a table with the specified name, that table's columns are returned. If pktable_owner is not specified and the current user does not own a table with the specified pktable_name, the procedure looks for a table with the specified pktable_name owned by the database owner. If one exists, that table's columns are returned.

Answer 3

Some good answers above. But I prefer to have the answer with one query. This piece of code is taken from sys.sp_helpconstraint (sys proc)

That's the way Microsoft looks up if there are foreign keys associated to the tbl.

--setup variables. Just change 'Customer' to tbl you want
declare @objid int,
    @objname nvarchar(776)
select @objname = 'Customer'    
select @objid = object_id(@objname)

if exists (select * from sys.foreign_keys where referenced_object_id = @objid)
    select 'Table is referenced by foreign key' =
        db_name() + '.'
        + rtrim(schema_name(ObjectProperty(parent_object_id,'schemaid')))
        + '.' + object_name(parent_object_id)
        + ': ' + object_name(object_id)
    from sys.foreign_keys 
    where referenced_object_id = @objid 
    order by 1

The answer will look like this: test_db_name.dbo.Account: FK_Account_Customer

Answer 4

SELECT
  object_name(parent_object_id),
  object_name(referenced_object_id),
  name 
FROM sys.foreign_keys
WHERE parent_object_id = object_id('Table Name')

Answer 5

I'd use the Database Diagramming feature in SQL Server Management Studio, but since you ruled that out - this worked for me in SQL Server 2008 (don't have 2005).

To get list of referring table and column names...

select 
    t.name as TableWithForeignKey, 
    fk.constraint_column_id as FK_PartNo, c.
    name as ForeignKeyColumn 
from 
    sys.foreign_key_columns as fk
inner join 
    sys.tables as t on fk.parent_object_id = t.object_id
inner join 
    sys.columns as c on fk.parent_object_id = c.object_id and fk.parent_column_id = c.column_id
where 
    fk.referenced_object_id = (select object_id 
                               from sys.tables 
                               where name = 'TableOthersForeignKeyInto')
order by 
    TableWithForeignKey, FK_PartNo

To get names of foreign key constraints

select distinct name from sys.objects where object_id in 
(   select fk.constraint_object_id from sys.foreign_key_columns as fk
    where fk.referenced_object_id = 
        (select object_id from sys.tables where name = 'TableOthersForeignKeyInto')
)

Answer 6

The original question asked to get a list of all foreign keys into a highly referenced table so that the table can be removed.

This little query returns all the 'drop foreign key' commands needed to drop all foreign keys into a particular table:

SELECT 
   'ALTER TABLE ['+sch.name+'].['+referencingTable.Name+'] DROP CONSTRAINT ['+foreignKey.name+']' '[DropCommand]'
FROM sys.foreign_key_columns fk
    JOIN sys.tables referencingTable ON fk.parent_object_id = referencingTable.object_id
    JOIN sys.schemas sch ON referencingTable.schema_id = sch.schema_id
    JOIN sys.objects foreignKey ON foreignKey.object_id = fk.constraint_object_id
    JOIN sys.tables referencedTable ON fk.referenced_object_id = referencedTable.object_id
WHERE referencedTable.name = 'MyTableName'

Example output:

[DropCommand]
ALTER TABLE [dbo].[OtherTable1] DROP CONSTRAINT [FK_OtherTable1_MyTable]
ALTER TABLE [dbo].[OtherTable2] DROP CONSTRAINT [FK_OtherTable2_MyTable]

Omit the WHERE-clause to get the drop commands for all foreign keys in the current database.