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What Do You Understand By A Foreign Key In Sql? |
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Answer» A foreign key is a field in a table, USED to create a link between TWO tables. It defined in one table but refer to the primary key of another table. A table which contains the foreign key is called the child table. And the table which includes the candidate key is called as parent table. Some important points for foreign key: A value for a foreign key can be NULL. All VALUES for foreign key should be present for all equivalent values of a primary key. A foreign key is a field in a table, used to create a link between two tables. It defined in one table but refer to the primary key of another table. A table which contains the foreign key is called the child table. And the table which includes the candidate key is called as parent table. Some important points for foreign key: A value for a foreign key can be NULL. All values for foreign key should be present for all equivalent values of a primary key. |
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