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Mapping in DBMS architecture?

We know that three view-levels are described by means of three schemas. These schemas are stored in the data dictionary. In DBMS, each user refers only to its own external schema. Hence, the DBMS must transform a request on. a specified external schema into a request against conceptual schema, and then into a request against internal schema to store and retrieve data to and from the database. The process to convert a request (from external level) and the result between view levels is called mapping. The mapping defines the correspondence between three view levels. The mapping description is also stored in data dictionary. The DBMS is responsible for mapping between these three types of schemas. There are two types of mapping. (i) External-Conceptual mapping (ii) Conceptual-Internal mapping External-Conceptual Mapping An external-conceptual mapping defines the correspondence between a particular external view and the conceptual view. The external-conceptual mapping tells the DBMS which objects on the conceptual level correspond to the objects requested on a particular user's external view. If changes are made to either an external view or conceptual view, then mapping must be changed accordingly. Conceptual-Internal Mapping The conceptual-internal mapping defines the correspondence between the conceptual view and the internal view, i.e. database stored on the physical storage device. It describes how conceptual records are stored and retrieved to and from the storage device. This means that conceptual-internal mapping tells the DBMS that how the conceptual! records are physically represented. If the structure of the stored database is changed, then the mapping must be changed accordingly. It is the responsibility of DBA to manage such changes.


High-Performance Oracle SQL Performance Tuning Tools for Databases?

database configuration monitoring, DBMS hardware configuration (a DBMS and related database may span computers, networks, and storage units) and related database mapping


What is the difference between a key and a superkey in DBMS?

I am supposing that key means primary key.Superkey is any subset of attributes that uniquely identifies the tuples of a relation. This subset need not be minimal, that is, one can remove some attributes from it and it is still uniquely identifying. If all redundant attributes are removed you get a subset what is called primary key.


When we are able to count the number of object we say we have a situation called?

In mathematics it is a situation where there is a one-to-one mapping with the set of counting numbers, Z, or a subset of Z.


Dbms and rdbms?

A DBMS (Database Management System) is a software application that allows users to interact with a database. An RDBMS (Relational Database Management System) is a type of DBMS that organizes data into tables with rows and columns, and uses structured query language (SQL) for querying and managing data. RDBMSs are a subset of DBMSs, designed specifically for relational databases.


What are highlights of DBMS?

NA_ what are highlights of advanced DBMS what are highlights of advanced DBMS what are highlights of advanced DBMS


Is java DBMS?

no, Java is not dbms.. Java is a programming language Dbms is database


Is SQL DBMS or RDBMS?

dbms


What are three types of dbms?

Hierarchical DBMSNetwork DBMSRelational DBMS


What is the difference between a subset and a proper subset?

the difference between a subset and a proper subset


What are the ASCII codes for subset and proper subset?

Since ASCII ⊊ unicode, I don't know if there are ASCII codes for subset and proper subset. There are Unicode characters for subset and proper subset though: Subset: ⊂, ⊂, ⊂ Subset (or equal): ⊆, ⊆, ⊆ Proper subset: ⊊, ⊊,


What is specialization in dbms?

Specialization in database management refers to the process of creating subtypes from a supertype entity in an entity-relationship (ER) model. It allows for the customization and organization of data based on unique characteristics within a specific subset of the main entity. This helps in categorizing and structuring data more efficiently.