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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:
Explain the two types of participation constraint. Total: The participation of an entity set E in a relationship set R is said to be total if each entity in E participates i
Explain the Recoverable Schedule A recoverable schedule is one in which for each pair of transactions Ti and Tj such that Tj reads a data item formerly written by Ti, the comm
Sub query in the UPDATE command : Example : //Double the commission for employees, who have got at least 2 increments. UPDATE EMP SET COMM = COMM * 2 WHERE
what should be included in this???
Define object-relational systems? Systems that give object-oriented extensions to relational systems are known as object-relational systems.
What is the role of a database administrator?
What is catalog in DBMS? Catalog - A relational DBMS maintains information about every table and index in which it contains. A catalog is a collection of special tables that st
Distributed Control and Data sharing: The geographical distribution of an organization can be showed in the distribution of the data; if a number of different sites are linked to e
State about the Tables- DBMS Data is stored in columns and rows (much like a spreadsheet -main difference is how data is organised). Every row in a table is known as a record
normal forms
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