DBMS Basics Flashcards
What is data
Facts about and entity that can be recorded or stored
What is information
Processed,meaningful and usable data
What is information
Processed,meaningful and usable data
What is Database
Collection of logically related data
Define Management
Manipulation,Searching and Security of Data
Define Database Management System
Set of programs or software used to define,manipulate, retrieve and manage data in a database.
DB+DBMS=
DB + DBMS = DBS (Database System)
Whats File processing System
- A file processing system is a software that stores and manage files in computer
hard disk. - It allows access to single files or tables at a time.
- Data is directly stored in set of files.
- It contains flat files that have no relation to other files.
- File system consists of different files which are grouped into directories.
The directories further contain other folders and files. - E.g. NTFS (New Technology File System), EXT (Extended File System)
Disadvantages file-processing system are!?
- Data redundancy and inconsistency
- Difficulty in accessing data
- Data isolation
- Integrity problems
Whats Data redundancy and inconsistency
- Redundancy occurs when same piece of the data is held in two or more separate places.
- Inconsistency occurs when same data is kept in different format or have different values at two or more places.
Whats Difficulty in accessing data
It does not allow needed data to be retrieved in a convenient and efficient manner
Whats Data isolation
Data is scattered in various files, and files may be in different formats.
Whats Integrity problems
The data values stored in the database must satisfy certain types of constraints.
What are the Characteristics of the Database Approach
- In the database approach, a single repository maintains data.
- It should be accessed by various users repeatedly through queries, transactions,
and application programs. - The main characteristics of the database approach are:
- Self-describing nature of a database system
- Insulation between programs and data, and data abstraction
- Support of multiple views of the data
- Sharing of data and multiuser transaction processing
What is Meta Data
The structure of each file, the type and storage format of each data item, and various constraints on the data.
This information is called meta-data.
Whats DBMS Architecture
- The DBMS design depends upon its architecture. The basic client/server architecture is used to
deal with a large number of PCs, web servers, database servers and other components that are
connected with networks. - This architecture consists of many PCs and a workstation which are connected via the network.
- DBMS architecture depends upon how users are connected to the database to get their
request done.
Types of DBMS Architectures are
1-Tier Architecture
2-Tier Architecture
3-Tier Architecture
Whats 1-Tier Architecture ?!
- The database is directly available to the user.
- Any changes done here will directly be done on the database itself. It doesn’t provide a handy tool for
end users. - The 1-Tier architecture is used for development of the local application, where programmers can
directly communicate with the database for the quick response.
Whats 2-Tier Architecture?!
The 2-Tier architecture is same as basic client-server. In the two-tier architecture, applications on the
client end can directly communicate with the database at the server side. For this interaction, API’s
like: ODBC, JDBC are used.
* The user interfaces and application programs are run on the client-side.
* To communicate with the DBMS, client-side application
establishes a connection with the server side.
Whats 3-Tier Architecture?
- The 3-Tier architecture contains another layer between the client and server. Here, client can’t directly communicate with the server.
- The application on the client-end interacts with an application server which further communicates with the database system.
- End user has no idea about the existence of the database beyond the application server. The database also has no idea about any other user beyond the application.
- The 3-Tier architecture is used in case of large web application.
Whats database schema!?
The description of a database is called the database schema.
* Includes descriptions of the database structure, data types, and the constraints
on the database.
* It is specified during database design and is not expected to change frequently.
* Each object in the schema—such as STUDENT or COURSE— called a schema
construct.
Whats Database state/snapshot
The data in the database at a particular moment in time is called a
database state or snapshot
* It changes every time we add new data in database.
* It is also called the current set of occurrences or instances in
the database.
Disadvantage of file processing system:
- Atomicity problems
- It is essential in database that either complete query to be executed, or none, which means
either all the operations in a transaction executes or none. - Concurrent-access anomalies
- For faster response, many systems allow multiple users to update the data simultaneously.
Whats three Schema Architecture
- Internal schema describes the physical storage structure and access paths.
- Typically uses a physical data model.
- Conceptual schema describes the structure and constraints for the whole database for different users.
- The conceptual schema hides the details of physical storage structures and focuses on describing entities, data types, relationships, constraints, etc.
- Uses a conceptual or an implementation data model.* External schemas (view schemas) describes the part of the database that a particular user is interested in and
hides the remaining database from that user group. - The view schema describes the end user interaction with database systems.
- Usually uses the same data model as the conceptual schema.
Whats Data abstraction
To ease the user interaction with database, the developers hide internal irrelevant
details from the users and provides abstract view of data to users. This process of
hiding irrelevant details from user is called Data Abstraction.
Whats Data Independence
Data independance means if we enter new data or update,rest of the data should not been displaced or disturbed
What is Cardinality Ratio
Cardinality Ratio: It defines minimum and maximum entity occurrences that participating in
a relationship.
Whats Weak entity set
Weak Entity Set
} Entity types that do not have any key attribute and can not be identified independently are called weak entity.
} The existence of a weak entity set depends on the existence of a strong entity set
} Entities belonging to a weak entity set are identified by being related to specific entities from another entity set in combination with one of their attribute values.
