The two principal rules for the relational model are as follows:

1. Entity integrity: this is used to maintain the integrity at entity level
2. REFERENTIAL integrity: it is used to maintain integrity on all the VALUES which have been referenced.

The differences between them are as follows:

• Entity integrity tells that in a database every entity should have a unique key; on the other hand referential integrity tells that in the database every table values for all foreign keys will remain valid.
• Referential integrity is based on entity integrity but it is not the other way around.

For example: if a table is PRESENT and there is a SET of column out of which one column has parent key set then to ensure that the table doesn’t contain any duplicate values, a unique index is defined on the column that CONTAINS the parent key.

The two principal rules for the relational model are as follows:

The differences between them are as follows:

For example: if a table is present and there is a set of column out of which one column has parent key set then to ensure that the table doesn’t contain any duplicate values, a unique index is defined on the column that contains the parent key.