How do I know if CONSTRAINT_NAME is a primary or foreign key?

Question

Using this SQL on SQL Server 2005

SELECT CONSTRAINT_NAME
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
WHERE TABLE_NAME = @TableName
  AND COLUMN_NAME=@ColumnName

I get primary keys and foreign keys.

How can I get only foreign keys? How can I find out if a constraint is a primary or a foreign key?

thanks

Answer 1

I used the following SQL with SQL Server 2005 to get the constraint names using the primary key:

SELECT Constraint_Name 
FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS 
WHERE UNIQUE_CONSTRAINT_NAME = 
   (SELECT CONSTRAINT_NAME 
    FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
    WHERE TABLE_NAME = @TableName AND COLUMN_NAME = @ColumnName)

To get the name of a foreign key constraint:

SELECT CONSTRAINT_NAME 
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
WHERE TABLE_NAME = @TableName AND COLUMN_NAME = @ColumnName

To get the table and foreign key field by constraint name:

SELECT TABLE_NAME, COLUMN_NAME 
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
WHERE CONSTRAINT_NAME = @ConstraintName

To get the table of the main field and the field by the name of the restriction:

SELECT TABLE_NAME, COLUMN_NAME 
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
WHERE CONSTRAINT_NAME = 
    (SELECT UNIQUE_CONSTRAINT_NAME 
     FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS 
     WHERE CONSTRAINT_NAME = @ConstraintName)

Answer 2

, , Pinal Dave

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

...

SELECT i.name AS IndexName,
        OBJECT_NAME(ic.OBJECT_ID) AS TableName,
        COL_NAME(ic.OBJECT_ID,ic.column_id) AS ColumnName
FROM sys.indexes AS i
        INNER JOIN sys.index_columns AS ic
        ON i.OBJECT_ID = ic.OBJECT_ID 
    AND i.index_id = ic.index_id
WHERE i.is_primary_key = 1

, :)

Answer 3

, -.

, .

select *

select constraint_name

, .

Answer 4

SELECT CONSTRAINT_NAME
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE
WHERE TABLE_NAME = @TableName
  AND COLUMN_NAME=@ColumnName
  AND REFERENCED_COLUMN_NAME IS NOT NULL

Answer 5

, MS SQL Server PK FK , - ...

SELECT CONSTRAINT_NAME 
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
WHERE TABLE_NAME = @TableName
AND LEFT(CONSTRAINT_NAME,2) = 'FK'

:)

When I tried to answer Quassnoi, I got an "Invalid column name" REFERENCED_COLUMN_NAME "error.

Answer 6

I am using something like this. It also works in SQL Server 2000.

select  object_name(fkx.constid) as fk_name,
        fkx.keyno as num,
        object_name(fkx.fkeyid) as child_table,
        col_name(fkx.fkeyid, fkx.fkey) as child_column,
        object_name(fkx.rkeyid) as parent_table,
        col_name(fkx.rkeyid, fkx.rkey) as parent_column
from sysforeignkeys fkx
order by fk_name, fkx.keyno

All this in system tables and views that are well documented.