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What are views? Explain how views are different from tables?
A view in SQL terminology is a one table in which is derived from other tables. These other tables could be base tables or previously described views. A view does not necessarily exist in physical form; it is considered a virtual table, in contrast to base tables, whose tuples are infact stored in the database. This limits the possible update operations in which can be applied to views, but it does not provide any limitations on querying a view. A view represents a variant perspective of a base relation(s). The definition of a view in a form view statement is stored in the system catalog. Any attribute in the view could be updated as long as the attribute is simple and not derived from a computation including two or more base relation attribute. View that includes a join may or may not be updatable. Such views are not updatable if they do not include the primary keys of the base relations.
Cardinality of Relationship One-to-One Only one entity of the first set is linked to only one entity of the second set. E.g. A teacher teaches a student. Only one teacher
Consider the following relational database: STUDENT (name, student#, class, major) COURSE (course name, course#, credit hours, department) SECTION (section identifier, course#, sem
Using Literal Character String Example: To print IS A as one string with column name employee SELECT ENAME || ' IS A ' || JOB AS "EMPLOYEE" FROM EMP;
Secondary Indexes Let consider the student database and its clustering index and primary (only one will be applicable at a time). Now consider the state when the database is to
Define Timestamp ordering Ans In timestamp-based method, a serial order is made among the concurrent transaction by assigning to every transaction a unique nondecreasing number
What is a Data Flow Diagram? Data Flow Diagram: A data flow diagram is the graph that shows flow of data values from their sources in objects in the course of processes whic
Recovery Techniques: After Reading the types of failures and database errors, let us talk about how to recover from the failures. Recovery can be complete using/restoring the previ
Describe the storage structure of indexed sequential files and their access method. Ans: Index offers a lookup capability to rapidly reach the vicinity of the desired record.
What will be create when a primary key if combined with a foreign key? A primary key if combined with a foreign key it creates Parent-Child relationship between the tables that
While sorting, if the main storage available is not enough, the system writes data to an external help file. The SAP profile parameter, which determines DIR_SORTTMP
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