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Define entity integrity and referential integrity. How does SQL allow specification of these?
Ans: Entity Integrity Rule- If the attribute A of relation R is a prime attribute of R after that A cannot accept null values.
Referential Integrity Rule- In referential integrity, it is made sure that a value that appears in one relation for a given set of attributes as well appears for a particular set of attributes in another relation.
In SQL, referential integrity and entity integrity rules are implemented as constraints on the relation known as reference Key constraint and primary Key constraint correspondingly.
These constraints can be fixed with relation at the time of creation of the relations or after the creation of the relations by altering the definition of the relations. For instance:
Column Constraints: NOT NULL, UNIQUE, CHECK, PRIMARY KEY, DEFAULT, REFERENCES, On delete Cascade : Using this key whenever a parent row is removed in a referenced
What is Hierarchical DBMS In HDBMS, data is structured in a tree like manner. There is a parent-child relationship between data items and the data model is very suitable for re
The State of NewYork certifies firefighters throughout state and keep track all of them, as well as of the state’s fire departments. Each fire department has unique department numb
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Explain data dictonary on oracle ? Data Dictionary - Data dictionaries are the system tables in which contain descriptions of the database objects and how they are structured.
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Define Aggregate functions and what aggregate functions supported by the MySQL To calculate a summary value from a set of individual values and uses one of the functions known
With the help of a suitable diagram gives module wise explanation of system architecture of DBMS.on..
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