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  They restrict invalid data entry in referenced fields and ensure updates in the master table are automatically
                 reflected in related tables.
                Relationships  save time by eliminating  the need to re-enter  data across connected tables, reduce
                 data-entry errors, and facilitate summarising data from related tables.

              Referential Integrity

              Referential integrity is applied in databases to maintain the accuracy and consistency of data in relationships
              between tables. When data is linked between two or more tables with the help of primary key and foreign
              key constraints, this rule helps to:
              Referential integrity ensures that you cannot add records to a child table (which contains the foreign key)
              unless  there  is  a  corresponding  parent  record  (which  contains  the  primary  key).  This  is  enforced  by  the
              foreign key constraint.

              Changing a primary key value in the parent table is generally not allowed as it would violate referential
              integrity. This is because foreign keys in child tables reference the primary key value.

              Referential integrity typically prevents deleting records from the primary key table if there are matching
              records in the child table(s), unless cascading delete is specified.

              Creating and Editing Relationships between Tables

              Consider a database of your class in which the student details and their marks details are stored in two
              separate Tables, namely, Student and Student_Marks. Establish a relationship between two tables and add a
              few records in both the tables. Delete a record from the Student table and see if the same gets deleted from
              the Student_Marks table or not.
              A relationship refers to an association or connection between fields of two or more tables. When you relate
              or connect two tables, there is a need to enter the same data in separate tables.

              The steps to create a relationship between tables are as follows:
              Step 1:  Click on the Tools menu in the Menu bar.
              Step 2:  Select the Relationships option from the drop-down menu to set up relationships.

                       The Relation Design window appears with the Add Tables dialog box.

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