Is it possible to list all foreign keys in a database?

Theoretically, this is hard. The relational model allows any field to relate to any other field. Which ones are actually used is defined by all possible SELECT statements that could be used.

Practically, it depends on how many tables have the FK definitions included. If someone bothered to carefully define all FK references -- and the SELECT statements stick to these rules -- you can query them.

However, since a SELECT statement can join on anything, there's no guarantee that you have all FK's unless you also have all SELECT statements.

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Edit.

See http://www.lostechies.com/blogs/jimmy_bogard/archive/2008/11/26/viewing-all-foreign-key-constraints-in-sql-server.aspx

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 
INNER JOIN sys.foreign_key_columns AS fc 
   ON f.OBJECT_ID = fc.constraint_object_id

Might work for you.

I use this statement, it seems to work pretty well.

SELECT RC.CONSTRAINT_NAME FK_Name
, KF.TABLE_SCHEMA FK_Schema
, KF.TABLE_NAME FK_Table
, KF.COLUMN_NAME FK_Column
, RC.UNIQUE_CONSTRAINT_NAME PK_Name
, KP.TABLE_SCHEMA PK_Schema
, KP.TABLE_NAME PK_Table
, KP.COLUMN_NAME PK_Column
, RC.MATCH_OPTION MatchOption
, RC.UPDATE_RULE UpdateRule
, RC.DELETE_RULE DeleteRule
FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS RC
JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE KF ON RC.CONSTRAINT_NAME = KF.CONSTRAINT_NAME
JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE KP ON RC.UNIQUE_CONSTRAINT_NAME = KP.CONSTRAINT_NAME