Constraints and Database Schemas Video Lecture - SSC CGL Tier 2 - Study

hello friends welcome back in this
tutorial we will study about constraints
on databases there are many restrictions
or constraints on the actual values in a
database state constraints on databases
can be divided into three categories
first is inherent model based
constraints or implicit constraints
these are the constraints that are
inherent in the data model for example
the constraint that a relation cannot
have duplicate tuples is an inherent
constraint of the relational model
second is a schema based constraints or
explicit constraints a schema based
constraints are explicit constraints are
constraints that can be directly
expressed in the schema of the data
model by specifying them in the DDL for
example key constraints domain
constraints and entity integrity
constraints are constraints that can be
expressed in a schema of the relational
model domain constraints are schema
based constraints of the relational
model domain constraints specify that
within each tuple the value of each
attribute a must be an atomic value from
the domain of attribute P
third is application-based
our semantic constraints these are the
constraints that cannot be directly
expressed in the schema of the data
model so they must be expressed and
enforced by the application programs
thank you very much