Chapter 2 Flashcards
Mainframe architecture
All computing intelligence resides within a powerful central host computer. The host computer processes the data and displays the output on “workstations” that have little to no processing power
Client- server architecture
- A network architecture in which each computer on the network is either a client or a server
- client: apiece of hardware/ software that makes requests of a more powerful server in order to utilize a shareable resource such as applications or data
-Server-takes requests from clients and shares its resources - cient-server is distributed computing
Two-tier architecture
Comprised of the server, (back-end application), and the client ( front end application)
Fat and thin clients and servers
- fat client: a client that handles the presentation logic and business logic
- thin server: handles the data access logic
- thin client: a client that handles only the presentation logic
- fat server: handles Th business and data access logic
Client-server logic
- presentation logic: software that displays data to the user and accepts input from the user. Manages the user navigation experience with a GUI
- Business Logic: programming logic that specifies how business transactions are processed and what data needs to be accessed from The data storage device
- data access Logic: refers to the communication with the database, which is responsible for data storage and retrieval on The physical storage device
Three- tier client server
- places one or more application tiers between the client tiers and the database tiers. Each tier contains code belonging to just that layer
-Advantages: better security, easier maintenance, scales more easily
Web based architecture
- The presentation layer is split into a web server and a web browser
- web serven-delivers content or services to and user over the internet
-Web browser: “talks” to a server and asks it for the pages the user wants to see
Relational database
-Most ERP systems access a RDBMS. Advantages: data is only entered once and shared across departments and business units, minimizing maintenance costs errors, and data duplication
- ERP systems can work with other databases such as in-memory database. More expensive than RDBMS because all data is stored in Ram
Database terminology
- Data on an entity (something that can be uniquely identified) is stored in a two-dimensional table, also known as a relation.
- A field (columns in The table) is designed to maintain certain information about every row in the table
- records (rows in the table) are groupings of related fields
Entity integrity
- A primary key (Pk) is the unique attribute that defines each record in a table
- The entity integrity rule is the mechanism the database uses to enforce unique pk’s in each table
- rules: pls is unique, pls may not be null
Table relationships
- A FK points to a the in a different table and establishes and enforces a link between the 2 tables
- an entity relationship diagram is a graphical representation reflecting the database entities and the relationships among those entities
- relationship is established between 2 when tales one table has an fle that references the PK of another table
- types of relationships: 1 to M, 1 to 1, M TO M
One to many relationship
An occurrence of one entity can be linked to more than one (many) occurrences of another entity. Very common
One to one relationship
Each record in a table is associated with only one occurrence in another table- least Common
Many to many relationship
An occurrence in one table is associated with more than one occurrence in a second table (and vice versa).
- RDBMS don’t allow many to many and thus a join on junction is needed table
Junction table
- each record in the junction table contains fk’s from the 2 tables it joins together
- these 2 fks become the Pk in the junction table in order to make each record in the table Unique
- the two pus in the join table are called the concatenated keys.
