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Using join indexes
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Example
In the sample database used throughout this book, the sales_order table
contains three foreign keys, each of which is related to the primary key of
another table.
You can create this table using the following commands:
CREATE TABLE "DBA"."sales_order"(
(
"id" integer NOT NULL,
"cust_id" integer NOT NULL
REFERENCES "DBA"."customer" ("id")
UNENFORCED,
"order_date" datetime NOT NULL,
"fin_code_id" char(2) NULL
REFERENCES "DBA"."fin_code" ("code")
UNENFORCED,
"region" char(7) NULL,
"sales_rep" integer NOT NULL
REFERENCES "DBA"."employee" ("emp_id")
UNENFORCED,
PRIMARY KEY ("id"),
);
As shown in the figure, the sales_order table is at the center of the star join.
Each of its foreign key columns can contain many instances of the primary key
it refers to. For example, if you enter: