Question

What integrity constraints are specified on database schema? Why is each
considered important?

Answer 1

Integrity constraints are specified on database schema

Explanation:

The following are various Integrity constraints specified on database schema:

Domain constraints

• Domain constraints for an attribute can be defined as specifying a specific set of values. Domain type data includes string, character, integer, time, date, currency, etc. The attribute value has to be available in the respective domain.

Entity integrity constraints

• The entity integrity constraint states that primary key value can't be null. This is because the primary key value is used to identify the relationship between individual rows, and if the primary key has a null value, then we cannot identify those rows.

Referential Integrity Constraints

• A referential integrity constraint is defined between two tables. In the Constraints on Referential Integrity, if a foreign key in Table 1 corresponds to the primary key in Table 2, then each value of the Foreign Key in Table 1 must be null or in Table 2.

Key constraints

• Keys are the entity set used to uniquely identify an object inside its entity set.  An entity set may have several keys but the primary key will be one of them. In the relational table, a primary key can contain a unique and null value.