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What is inheritance? Define it in detail?
Inheritance
Inheritance can be at the levels of types, or at the level of tables we first consider inheritance of types, then inheritance at the level of labels.
Type inheritance
Assume that we have the following type definition for people
create type person
(name varchar(20)
address varchar(20))
Table inheritance
Create table people of person
The consistency requirements for sub tables are
1. Each tuple of the sub table can correspond to at most single tuple in each of its immediate sub tables.
2. SQL:1999 has an additional constraint that all the tuples corresponding to each other must be derived from single tuple .
What is key ? Key - A single attribute or a combination of two or more attributes of an entity set which is used to recognize one or more instances (rows) of the set (table) is
The physical location of a record is determined by which mathematical formula that transforms a file key into a record location? The physical location of a record is determined
What is a data dictionary? Data Dictionary is a main source of data in a data management system. Its major function is to carry the creation and management of data definition
Example : Search the name, department number and salary of employees drawing minimum salary in that department. SELECT ENAME, SAL, DEPTNO FROM EMP WHERE SAL IN (SELECT MI
Explain in details about the f unctions of DBA ?
Define in which normalisation form if an attribute of a composite key is dependent on an attribute of other composite key. Ans: 3NF A relation is in 3 NF if an attribute of
Association as a cache This association must be updated when any new element is added to it, but testing for overlap using association is more efficient. Figure:
The Second Normal Form (2NF) Definition: A relation is in 2NF if it is in 1NF and each non-key attribute is fully dependent on each candidate key of the relation. Some of th
Meaningful use refers to the use of certified EHR technology to "enhance quality, efficiency, and reduce health disparities
Backward Recovery (UNDO): In this system the uncommitted changes made by a transaction to a database are undone. Instead the system is reset to the last consistent state of databa
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