Key Constraints and NULL Value Constraints || Lesson 31 || DBMS || Learning Monkey ||
Key Constraints and NULL Value Constraints
In this class, we will understand Key Constraints and NULL Value Constraints.
We have already discussed the concepts of domain constraints.
Key Constraints and NULL Value Constraints
Key Constraints
To understand this, let us consider the simple table given below.
Why should we have the ‘key’ constraint?
If we consider an employee table, every employee is unique.
We should repeat the details of the employee.
We have to identify an attribute for a table that should have all unique values for that unique identification.
The definition of a relation states that a Relation is defined as a Set of Tuples.
The definition of a set from our primary math states that all elements of the set are distinct.
For example, the set of natural numbers will not have repetitions.
{1, 2, 3, 4, 5, …..}.
NULL value constraints
To understand this, let us consider the simple table given below.
In the above table, the name of the employee should not be NULL.
There will not be an employee who does not have a name.
So we should not accept the details of the employee without a name on the table.
#learningmonkey #dbms #placements #gatecse #gatedbms #campusplacements
Link for playlists:
/ @learningmonkey
Link for our website: https://learningmonkey.in
Follow us on Facebook @ / learningmonkey
Follow us on Instagram @ / learningmonkey1
Follow us on Twitter @ / _learningmonkey
Mail us @ [email protected]
In questa pagina del sito puoi guardare il video online Key Constraints and NULL Value Constraints || Lesson 31 || DBMS || Learning Monkey || della durata di ore minuti seconda in buona qualità , che l'utente ha caricato Learning Monkey 20 ottobre 2021, condividi il link con amici e conoscenti, su youtube questo video è già stato visto 2,217 volte e gli è piaciuto 36 spettatori. Buona visione!
