Dealing with constraints violation, Database Management System

Assignment Help:

If the deletion violates referential integrity constraint, then three alternatives are available:

Default option: - refuse the deletion. It is the job of the DBMS to describe to the user why the deletion was rejected.
Attempt to propagate (or cascade) the deletion by deleting tuples that reference the tuple that is being deleted.
Vary the value of referencing attribute that origins the violation.

Example:

Let R:

A#	B	C^
A1	B1	C1
A2	B3	C3
A3	B4	C3
A4	B1	C5

C#	D
C1	D1
C3	D2
C5	D3

Note:

1) '#' shows the Primary key of a relation.

2) '^' shows the Foreign key of a relation.

(1) Delete a tuple with C# = 'C1' in Q.

Violated constraint: - Referential Integrity constraint

Motive: - Tuples in relation A refer to tuple in Q.

Dealing: - Options available are

1) Decline the deletion.

2) DBMS may automatically delete all tuples from relation S and Q with C

# = 'C1'. This is known as cascade detection.

3) The one more option would result in putting NULL value in R where C1 exist, which is the initial tuple R in the attribute C.

Related Discussions:- Dealing with constraints violation

Three level architecture, explain external view

explain external view

Define one-way associations using pointers, One-way Associations If an...

One-way Associations If an association is only traversed in single direction, then it is known as one-way association. It is implemented as a pointer or an attribute which con

Extended e-r features, Although, the essential features of E-R diagrams are...

Although, the essential features of E-R diagrams are enough to design many database situations. Though, with more difficult relations and advanced database applications, it is need

Database tables design and test queries, Load sample data into the database...

Load sample data into the database tables design and test queries to return the following information • All rows and columns for employees • All rows and columns for customers •

Binary relationships, One-to-one relationship: For every 1:1 relationshi...

One-to-one relationship: For every 1:1 relationship type R in the ER diagram including two entities E1 and E2 we take one of entities (say E1) preferably with total participatio

Er diagram of textile industry, complete er diagram of textile industry man...

complete er diagram of textile industry management

Draw the E/R diagrams, for the following business rules . Identify all enti...

for the following business rules . Identify all entities, attributes, relationships, primary keys, cardinalities and constraints where appropriate 3. (9) An art museum owns a larg

Define direct file organization, Define Direct file organization? The d...

Define Direct file organization? The direct file organization is employed to enhance the performance in accessing the records than sequential file organization. In direct file

Sorting field groups we cannot use more than one key field, While sorting f...

While sorting field groups we cannot use more than one key field False.

Define deadlock detection, Define Deadlock detection If a system does ...

Define Deadlock detection If a system does not employ a few protocols that make sure deadlock freedom, after that a detection and recovery scheme should be used. An algorithm

Write Your Message!

Name

Email id

Message

Verfication Code

User Account

All Pages