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Explain the concept of a data model ?
Data Model - Model is an abstraction procedure which hides irrelevant details although highlighting details relevant to the applications at hand. As same, a data model is a collection of concepts which can be used to elaborate structure of a database and gives the essential means to achieve this abstraction. Structure of database means the data types, relationships, and constraints which should hold for the data. In common a data model consists of two elements:
• A mathematical notation for expressing relationships and data.• Operations on the data which serve to express queries and other manipulations of the data.
Consider the following frequency counts of some itemsets in a transaction database r : freq({A}, r) = 0.405 freq({B}, r) = 0.510 freq({C}, r) = 0.303 freq({A
The Conceptual Level or Global level The conceptual level presents a logical view of the complete database as a unified whole. It permits the user to bring all the data in th
Strict 2PL :Though, this basic 2PL suffers from the trouble that it can result into loss of isolation / atomic property of transaction as theoretically speaking once a lock is rele
#queDefine a job scheduling strategy that will meet business requirement of reporting availability by 6am CST for the following cubes? Show the job scheduling dependencies in a pic
Multiple column Queries: Syntax: SELECT COLUMN1, COL2,...... FROM TABLE WHERE (COLUMN1, COL2, ...) IN (SELECT COLUMN1, COL2,.... FROM TABLE WHERE );
Explain the function of input controls. Identify four types of input control and explain the function of each. Provide an example of a data integrity error that could occur i
What is Candidate Key Super Key or Candidate Key: It is such an attribute of a table that can uniquely recognize a row in a table. Generally they have unique values and can n
Explain the two types of participation constraint. 1. 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
Differentiate between natural join and outer join? Natural join is a binary operator which is written as (R * S) where as R and S are relations. The output of the natural join
State about the Activity Diagram Activity diagrams show flow from one activity to other. It is an ongoing non atomic execution within a state machine. Activity finally results
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