Sql 需要约束的表。 Relationships ---------------------------------------- aID aID_role bID bID_role ---------------------------

需要约束的表。

Relationships
----------------------------------------
aID     aID_role     bID     bID_role
----------------------------------------
 4        1           5        2

Relationships
----------------------------------------
aID     aID_role     bID     bID_role
----------------------------------------
 4        1           5        2
 5        2           4        1 <-- sort of a duplicate

CREATE VIEW dbo.Relationships_DRI_Unique
WITH SCHEMABINDING
AS
    SELECT
         CASE WHEN FromID < ToID THEN FromID ELSE ToID   END as Col1,
         CASE WHEN FromID < ToID THEN ToID   ELSE FromID END as Col2
    FROM
        dbo.Relationships
GO
CREATE UNIQUE INDEX IX_Relationships_DRI_Unique on dbo.Relationships_DRI_Unique (Col1,Col2)

id1 AS (CASE WHEN aID < bID THEN aid ELSE bid END),
id2 AS (CASE WHEN aID < bID THEN bid ELSE aid END),

aID  bID  id1  id2
4    5    4    5
5    4    4    5

CONSTRAINT IX_Relationships UNIQUE (id1, id2)

table persons
id PK
first_name,
second_name


table roles
id PK
role_id
role_name (ex. Father, daugther,)

table relationship
id PK
person    (ex. persons.id = 1, JOHN)
role      (roles.id = 5, FATHER
person_to (persons.id = 3, CARLA,