SQL-ForeignKeyConstraint-Page6
👉 Foreign Key Constraint Foreign Key represent relationships between tables. A foreign key is a column or group of columns whose values are derived from the primary key or unique key of some other table. ✅ The table in which the foreign key is defined is called Foreign table or Detail table. ✅ The table that defines the primary or unique key and is referenced by the foreign key is called the Primary table or Master table. 👉 Features 1)Master table cannot be updated if child records exists. 2)Records cannot be inserted or deleted into a detail table if corresponding records in the master table do not exist. 3)Records of the master table cannot be deleted if corresponding records in the detail table already exist. 👉 O...
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