To View All Constrains of a database

Before Script these are the one line description of information_schema which will use.

• INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS

Returns one row for each FOREIGN KEY constraint in the current database.

• INFORMATION_SCHEMA.TABLE_CONSTRAINTS

Returns one row for each table constraint in the current database.

• INFORMATION_SCHEMA.KEY_COLUMN_USAGE

Returns one row for each column that is constrained as a key in the current database.

Script to list down all constraints of a database is: 

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='something'WHERE FK.TABLE_NAME='something'
--WHERE PK.TABLE_NAME IN ('one_thing', 'another')
--WHERE FK.TABLE_NAME IN ('one_thing', 'another')

Source of this script is:
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/