SQL Multiple Foreign Keys as Primary Keys

Question

If I declare the table below does it implicitly imply that both the foreign keys make a unique primary key or do I need to do something more to make both attributes as a primary key?

CREATE TABLE Report_has_Items
(
    ReportID int REFERENCES Report(ReportID) NOT NULL,
    ItemID int REFERENCES Item(ItemID) NOT NULL
)

Essentially both attributes which are foreign keys from other tables, together would form a unique key.

Answer 1

No it doesn't. The above table has no primary key. If you want to use the fields as a primary key use:

CREATE TABLE Report_has_Items(
    ReportID int REFERENCES Report(ReportID) NOT NULL,
    ItemID int REFERENCES Item(ItemID) NOT NULL,
    PRIMARY KEY (ReportID, ItemID)
)

or something similar depending on your sql dilect.

Answer 2

Let's name our constraints, eh?

CREATE TABLE dbo.Report_has_Items(
    ReportID int NOT NULL,
       CONSTRAINT [FK_RHI_Report] (ReportId) REFERENCES dbo.Report(ReportID),
    ItemID int NOT NULL,
       Constraint [FK_RHI_Item] (ItemId) REFERENCES dbo.Item(ItemID),
    CONSTRAINT [PK_RHI] PRIMARY KEY (ReportID, ItemID)
)

Answer 3

I am not sure i understand your question completely but i assume you are trying to create a composite primary key (primary key with more than one attribute). You could do the following.

CREATE TABLE Report_has_Items(
  ReportID int references Report(ReportID),
  ItemID int references Item(ItemID),
  PRIMARY KEY (ReportID , ItemID )
);

Note :The pair (ReportID , ItemID ) must then be unique for the table and neither value can be NULL.

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