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Database Systems Fundamentals: Three-Schema, Independence, and Languages, Cheat Sheet of Database Management Systems (DBMS)

Fundamentals of Database Systems. Three-Schema Architecture & Data Independence DBMS Languages, Interfaces & Classification Database System Environment

Typology: Cheat Sheet

2022/2023

Uploaded on 04/15/2023

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Index
Fundamentals of Database Systems.
Three-Schema Architecture & Data Independence
DBMS Languages, Interfaces & Classification
Database System Environment
Fundamentals of Database Systems.
A data model is a collection of concepts used to describe the structure of a database like
specifying the data types, constraints etc.. MOst data models include a set of basic
operations to manipulate the data in the database. Like retrieval of data from the database
or updates on the data.. THe first category of data models is the high-level or conceptual
data model, then we have the representational or implementation data models and finally
low level or physical data models.. Database schema database schema is a description of a
database and metadata is a subset of metadata or it is one of the components of metadata.
THe data in the database at a particular moment in time is called as a database state or an
instance or snapshot. Each object. Within the database is called a schema construct like for
example the tables in database student course etc. These are called as schemas construct..
Three-Schema Architecture & Data Independence
The goal of this three schemas architecture is to separate the user applications and the
physical database.. schemas can be defined at three levels. The first level is the internal
level. This internal level has an internal schemas. the next level in our three schema
architecture is the conceptual level. each external schemas describes the part of the
database that a user is interested in and hides the other database from the user group..
data independence can be defined as the capacity to change the schemas at one level of a
database system without having to. change the schema at one. level. without data
independence. If we make any changes at the internal level or to the internal. schemas,
then we have to change higher levels too but with data. independence when we change the
schema at. one level, it does n't affect the schemas at higher levels. Schemas do n't change
frequently, but if required to change with this concept of data independence, any changes
will not affect the higher levels. called as mapping..
DBMS Languages, Interfaces & Classification
There is no clear separation between the conceptual and the internal schemas. for each
database users. We have different interfaces and languages provided by the DbMs for each
of these users.. This is all about the languages provided by DbMs that is the data definition
language and storage definition language. the programming language that is embedded in
the programming language is called the data sub language and a high-level DMl is also called
set at a time DMl because it can retrieve many records in a single DMl statement itself. the
formbased interfaces are designed and programmed for the nave users or parametric
users.. There are several criteria used to classify database management systems, so the
criterias could be based on data. model number of users, cost of DbMs, number of sites,
types of access path, generality and so on. We will briefly look into few of these criteria. the
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Index

  • Fundamentals of Database Systems.
  • Three-Schema Architecture & Data Independence
  • DBMS Languages, Interfaces & Classification
  • Database System Environment Fundamentals of Database Systems. A data model is a collection of concepts used to describe the structure of a database like specifying the data types, constraints etc.. MOst data models include a set of basic operations to manipulate the data in the database. Like retrieval of data from the database or updates on the data.. THe first category of data models is the high-level or conceptual data model, then we have the representational or implementation data models and finally low level or physical data models.. Database schema database schema is a description of a database and metadata is a subset of metadata or it is one of the components of metadata. THe data in the database at a particular moment in time is called as a database state or an instance or snapshot. Each object. Within the database is called a schema construct like for example the tables in database student course etc. These are called as schemas construct.. Three-Schema Architecture & Data Independence The goal of this three schemas architecture is to separate the user applications and the physical database.. schemas can be defined at three levels. The first level is the internal level. This internal level has an internal schemas. the next level in our three schema architecture is the conceptual level. each external schemas describes the part of the database that a user is interested in and hides the other database from the user group.. data independence can be defined as the capacity to change the schemas at one level of a database system without having to. change the schema at one. level. without data independence. If we make any changes at the internal level or to the internal. schemas, then we have to change higher levels too but with data. independence when we change the schema at. one level, it does n't affect the schemas at higher levels. Schemas do n't change frequently, but if required to change with this concept of data independence, any changes will not affect the higher levels. called as mapping.. DBMS Languages, Interfaces & Classification There is no clear separation between the conceptual and the internal schemas. for each database users. We have different interfaces and languages provided by the DbMs for each of these users.. This is all about the languages provided by DbMs that is the data definition language and storage definition language. the programming language that is embedded in the programming language is called the data sub language and a high-level DMl is also called set at a time DMl because it can retrieve many records in a single DMl statement itself. the formbased interfaces are designed and programmed for the nave users or parametric users.. There are several criteria used to classify database management systems, so the criterias could be based on data. model number of users, cost of DbMs, number of sites, types of access path, generality and so on. We will briefly look into few of these criteria. the

most popular data model used today is the relational data model.. the object-oriented database model represents database as a collection of tables, having fields or attributes.. Database System Environment the different component modules in dbms let us look into each of these modules in detail. In addition to these modules most database management systems have database system utilities that help the database administrator to manage the system. The common utilities have the following types of functions so the common utilities are used to load existing data files into the database. The backup utility creates a backup copy of the database and with this backup copy we can restore the database in case of any kind of system failures. The next type of utility that we have is the file reorganization utility this utility is used to reorganize a database file into a different file organization.