4.1 KiB
4.1 KiB
- #CT230 - Database Systems I
- No previous topic
- Next Topic: The Relational Model
- Relevant Slides:
- What is a database? #card
card-last-interval:: 64.01
card-repeats:: 5
card-ease-factor:: 2.52
card-next-schedule:: 2023-01-24T13:09:54.692Z
card-last-reviewed:: 2022-11-21T13:09:54.692Z
card-last-score:: 5
- A database is ^^a collection of related data.^^
- What is the Database Approach? #card
card-last-interval:: 7.76
card-repeats:: 3
card-ease-factor:: 1.94
card-next-schedule:: 2022-11-22T10:36:04.634Z
card-last-reviewed:: 2022-11-14T16:36:04.634Z
card-last-score:: 3
- A single repository of data (which may be distributed) is maintained that is defined once and then accessed by various users via a DBMS.
-
Database Management Systems
- What is a DBMS? #card
card-last-interval:: 19.01
card-repeats:: 4
card-ease-factor:: 2.18
card-next-schedule:: 2022-12-03T16:40:07.862Z
card-last-reviewed:: 2022-11-14T16:40:07.862Z
card-last-score:: 5
- The DataBase Management System (DBMS) is a collection of programs that facilitates the process of ^^defining, constructing, & manipulating^^ databases for various applications.
-
DBMS Capabilities #card
card-last-interval:: 19.01 card-repeats:: 4 card-ease-factor:: 2.18 card-next-schedule:: 2022-12-03T16:44:40.304Z card-last-reviewed:: 2022-11-14T16:44:40.304Z card-last-score:: 3-
- Define database (DDL)
- Manipulate database (SQL)
- Control redundancy
- Restrict unauthorised access
- Enforce integrity constraints
- Provide multiple user interfaces / views
- Provide concurrent access
- Provide mechanism for recovery
- Provide back-up
- Allows representation of complex relationships between data (For efficiency & optimisation reasons)
-
-
Disadvantages of DBMS approach #card
card-last-interval:: 23.43 card-repeats:: 4 card-ease-factor:: 2.42 card-next-schedule:: 2022-12-08T02:39:24.701Z card-last-reviewed:: 2022-11-14T16:39:24.701Z card-last-score:: 3- Strict schema & multiple tables / relations
- Complexity
- Size
- Cost of DBMS
- Additional hardware costs
- Cost of conversion
- Performance
- Higher impact of failure
-
DBMS Users #card
card-last-interval:: 7.76 card-repeats:: 3 card-ease-factor:: 1.94 card-next-schedule:: 2022-11-22T10:36:32.717Z card-last-reviewed:: 2022-11-14T16:36:32.718Z card-last-score:: 3- Administrators (DBA) - accounts, passwords, privileges. Requiring constant vigilance
- System Analysts - "What's required to solve a problem? What does the business need?"
- Designers - ER diagrams, mapping ER diagrams to tables
- Application Programmers - creating tables, adding data, creating queries
- End users
- What is a DBMS? #card
card-last-interval:: 19.01
card-repeats:: 4
card-ease-factor:: 2.18
card-next-schedule:: 2022-12-03T16:40:07.862Z
card-last-reviewed:: 2022-11-14T16:40:07.862Z
card-last-score:: 5
- What is Database Abstraction? #card
card-last-interval:: 33.96
card-repeats:: 5
card-ease-factor:: 2.04
card-next-schedule:: 2022-12-18T19:23:19.167Z
card-last-reviewed:: 2022-11-14T20:23:19.167Z
card-last-score:: 3
- Database Abstraction refers to the hiding of the details of data storage that are not needed by most database users.
- The aim is to separate user's views of the database from the way that it is "physically" represented.
- 3 ways in which data can be described:
- External: user's view
- Conceptual: logical structure as seen by DBA
- Internal: DBMS and OS view of data
- What is the database schema? #card
card-last-interval:: 4
card-repeats:: 2
card-ease-factor:: 2.52
card-next-schedule:: 2022-11-18T20:24:46.045Z
card-last-reviewed:: 2022-11-14T20:24:46.046Z
card-last-score:: 5
- The database schema is the ^^logical structure of the database.^^
- What is the database instance? #card
card-last-interval:: 33.64
card-repeats:: 4
card-ease-factor:: 2.9
card-next-schedule:: 2022-12-18T11:00:02.004Z
card-last-reviewed:: 2022-11-14T20:00:02.004Z
card-last-score:: 5
- The database instance is ^^the actual content of the database at some point in time.^^
