1º - lets create a simple table, with a primary key field:
create table __TableName__
(
Field_Id int,
Name nvarchar(20),
constraint __PK_Name__ primary key (Field_Id),
constraint __FK_Name__ foreign key (Field_Id) references __ReferencedTable__
)
- in this example, the field "Field_Id" is a primary key in a foreign table, and for some reason, we need it to be unique at this table to,
- after add the PK, we should add the FK, in this way, we guarantee that no one can delete the row in the "__ReferencedTable__" WHEN, there is a row at this table with that "Field_Id"
2º - creating a table with 2 or more primary keys, that are from foreign tables:
create table __TableName__
(
Field_Id int,
Field2_Id int,
constraint __PK_Name__ primary key (Field_Id,Field2_Id),
constraint __FK_Name1__ foreign key (Field_Id) references __ReferencedTable__,
constraint __FK_Name2__ foreign key (Field2_Id) references __ReferencedTable2__
)
hope it helps
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