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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.
What is Multivalued Attribute? Multivalued Attribute - Multivalued attribute might have more than one value for an entity. For instance, PreviousDegrees of a STUDENT.
The External or View Level The external or view level is the highest level of abstraction of database. It gives a window on the conceptual view, which permits the user to see
What is system catalog or catalog relation? How is better known as? A RDBMS maintains a explanation of all the data that it contains, information about every relation and index
Example : Create a sequence named SEQSS that starts at 105, has a step of 1 and can take maximum value as 2000. CREATE SEQUENCE SEQSS START WITH 105 INCREMENT BY 1 MAX VA
Define a relation ? Relation - A relations is a named two-dimensional table of data. Mathematically, a relation can be described as a subset of the cartesian product of a lis
Text Processing: Use readLines to read SOU.txt into R. Create a vector called Pres containing the names of the presidents giving each speech. To do this, rst identify the lin
Write a query that display ename annual salary and comm from emp table
Natural Join : It is the similar like Equi join except one of the duplicate columns is removed in the result table. The natural join is the most usually used form of join operation
Creation of Indexes Automatically: When a primary key or Unique constraint is show in a table definition then a unique index is formed automatically. Manually: User can
Automated system for appointment with sms and call confirmation with service providers and user has to be initiate automatically. After selecting time and date to use service, s
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