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It can be easily defined as:
The database must not have any unmatched foreign key values.
The term "unmatched foreign key value" means a foreign key value for which there does not exist a matching value of the relevant candidate key in the relevant target (referenced) relation. For instance, any value existing in the EMPID attribute in ASSIGNMENT relation must be in the EMPLOYEE relation. That is, the only EMPIDs that can be in the EMPLOYEE relation are 101, 102 and 103 for the instance / present state of the database given in Figure. If we want to insert a tuple with EMPID value 104 in the ASSIGNMENT relation, it will cause violation of referential integrity constraint. Logically it is very obvious after all the employee 104 does not be, so how can s/he be assigned any work.
prototype of a distributed information system for a national car part retail outlet chain.
Synonyms It allows short names or alternative names for objects. Example : CREATE SYNONYM D30 FOR EMPD30; Now if we give command:
Modify a sequence: ALTER SEQUENCE SEQSS INCREMENT 2 MAXVALUE 3000; Removing a sequence: DROP SEQUENCE SEQSS;
What is a virtual table that draws its data from the result of an SQL SELECT statement? View is a virtual table that draws its data from the result of an SQL SELECT statement.
Consider an information system designed for an online company which provides IT products and services These include desktops, laptops, networking products, IT books, parts, and
Why containment is important in oosystems? Containment is an significant concept in oosystems because it allows dissimilar users to view data at different granularities.
What is first normal form? The domain of attribute must contain only atomic (simple, indivisible) values.
In an organisation various projects are undertaken. Each projects can employ one or more employees. Every employee can work on one or more projects. Each project is undertaken on
What are domain constraints? A domain is a set of values that might be assigned to an attribute .all values that appear in a column of a relation must be taken fro
What is object identity? An object retains its identity even if some or all the values of variables or explanations of methods change overtime.
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