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Explain Record Based Logical Models?
Record-Based logical Models: Also define data at the conceptual and view levels. Unlike object-oriented models, are used to state overall logical structure of the database, and gives a higher-level description of the implementation. Named so since the database is structured in fixed-format records of various types. Each record type defines a fixed number of fields, or attributes. Each field is commonly of a fixed length (this simplifies the implementation). Record-based models do not involved a mechanism for direct representation of code in the database. Separate languages related along with the model are used to express database queries and updates. The three most widely-accepted models are the relational, network, and hierarchical.
Hierarchical model is also known by? A hierarchical model is also known as a Tree structure.
Describe Physical Data independence ? Physical Data Independence - It is capacity to modify the internal schema without having to change conceptual schema. Therefore, the exter
What is horizontal fragmentation? Horizontal fragmentation divides the relation by assuming every tuple of r to one or more fragments
Multilevel Index The Multilevel Index is a modification of the secondary level index system. In this system we might be use even more number of levels in case the table is eve
BCNF Boyce-Codd Normal Form A relation schema R is in BCNF if it is in 3NF and accepts an additional constraint that for every FD X A, X has to be a candidate key. If a relati
What is the max. no. Of structures that can be included in a table or structure. Nine.
Explain the concept of QBE? Query-by-example represents a visual/graphical approach for accessing information in a database by the use of query templates called as skeleton tab
Describe integrity and security? a) Domain constraint b) Referential integrity A value that appears in one relation for a given set of attributes also appear fo
If R1 and R2 are two relations or functions, then the result of R3 = R1 × R2 is the combination of tuples that are in R1 and R2. The product is associative and commutative. Degr
What is a SELECT operation? The select operation selects tuples that please a given predicate. We use the lowercase letter σ to denote selection.
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