Quick Guide For SQL by Mehta Heer & Verma Prince

Author:Mehta, Heer & Verma, Prince
Language: eng
Format: epub
Publisher: Edignite NGO
Published: 2022-01-02T00:00:00+00:00

and

ALTER TABLE table_name

ADD CONSTRAINT constraint_name

FOREIGN KEY(column_name) REFERENCES tablename(column_name);

To set the Foriegn Key in orders table, we would need to execute the following command: -

ALTER TABLE orders ADD CONSTRAINT cost_to_orders FOREIGN KEY(cost_id) REFERENCES costumers(cost_id);

Upon describing the table, it will give the following output.

Here, we now have MUL in the key column corresponding to cost_id.

Joins in SQL

Sometimes we need to represent the data of two inter-related tables at once. This can be done by Joins.

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