How can I find out what FOREIGN KEY constraint references a table in SQL Server?

Question

I am trying to drop a table but getting the following message:

Msg 3726, Level 16, State 1, Line 3
Could not drop object \'dbo.UserProfile\' bec

Answer 1

You could use this query to display Foreign key constaraints:

SELECT
K_Table = FK.TABLE_NAME,
FK_Column = CU.COLUMN_NAME,
PK_Table = PK.TABLE_NAME,
PK_Column = PT.COLUMN_NAME,
Constraint_Name = C.CONSTRAINT_NAME
FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS C
INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS FK ON C.CONSTRAINT_NAME = FK.CONSTRAINT_NAME
INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS PK ON C.UNIQUE_CONSTRAINT_NAME = PK.CONSTRAINT_NAME
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE CU ON C.CONSTRAINT_NAME = CU.CONSTRAINT_NAME
INNER JOIN (
SELECT i1.TABLE_NAME, i2.COLUMN_NAME
FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS i1
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE i2 ON i1.CONSTRAINT_NAME = i2.CONSTRAINT_NAME
WHERE i1.CONSTRAINT_TYPE = 'PRIMARY KEY'
) PT ON PT.TABLE_NAME = PK.TABLE_NAME
---- optional:
ORDER BY
1,2,3,4
WHERE PK.TABLE_NAME='YourTable'

Taken from http://blog.sqlauthority.com/2006/11/01/sql-server-query-to-display-foreign-key-relationships-and-name-of-the-constraint-for-each-table-in-database/

Answer 2

I found this answer quite simple and did the trick for what I needed: https://stackoverflow.com/a/12956348/652519

A summary from the link, use this query:

EXEC sp_fkeys 'TableName'

Quick and simple. I was able to locate all the foreign key tables, respective columns and foreign key names of 15 tables pretty quickly.

As @mdisibio noted below, here's a link to the documentation that details the different parameters that can be used: https://docs.microsoft.com/en-us/sql/relational-databases/system-stored-procedures/sp-fkeys-transact-sql

Answer 3

Try this

SELECT
  object_name(parent_object_id) ParentTableName,
  object_name(referenced_object_id) RefTableName,
  name 
FROM sys.foreign_keys
WHERE parent_object_id = object_id('Tablename')

Answer 4

I am using this script to find all details related to foreign key. I am using INFORMATION.SCHEMA. Below is a SQL Script:

SELECT 
    ccu.table_name AS SourceTable
    ,ccu.constraint_name AS SourceConstraint
    ,ccu.column_name AS SourceColumn
    ,kcu.table_name AS TargetTable
    ,kcu.column_name AS TargetColumn
FROM INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE ccu
    INNER JOIN INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS rc
        ON ccu.CONSTRAINT_NAME = rc.CONSTRAINT_NAME 
    INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE kcu 
        ON kcu.CONSTRAINT_NAME = rc.UNIQUE_CONSTRAINT_NAME  
ORDER BY ccu.table_name

Answer 5

Here is the best way to find out Foreign Key Relationship in all Database.

exec sp_helpconstraint 'Table Name'

and one more way

select * from INFORMATION_SCHEMA.KEY_COLUMN_USAGE where TABLE_NAME='Table Name'
--and left(CONSTRAINT_NAME,2)='FK'(If you want single key)

Answer 6

You can also return all the information about the Foreign Keys by adapating @LittleSweetSeas answer:

SELECT 
   OBJECT_NAME(f.parent_object_id) ConsTable,
   OBJECT_NAME (f.referenced_object_id) refTable,
   COL_NAME(fc.parent_object_id,fc.parent_column_id) ColName
FROM 
   sys.foreign_keys AS f
INNER JOIN 
   sys.foreign_key_columns AS fc 
      ON f.OBJECT_ID = fc.constraint_object_id
INNER JOIN 
   sys.tables t 
      ON t.OBJECT_ID = fc.referenced_object_id
order by
ConsTable