Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
11 Cards in this Set
- Front
- Back
|
A Relational Model
|
The basic data structure is a table with the rows representing entities (e.g., a customer) and the columns representing the various attributes of the entity (e.g., name, address, and email address)
|
|
|
Data Integrity Problem
|
can occur only if data are duplicated.
|
|
|
row entity record
|
column attribute field
|
|
|
column attribute field,
|
is a column that identifies a unique row in a table Supplier_Number)
|
|
|
A (primary) key
|
is a column that identifies a unique row in a table
|
|
|
A compound key
|
is a group of columns that identifies a unique row in a table
|
|
|
A foreign key
|
is a key of a different or foreign table
|
|
|
Normalization
|
converting a poorly structured table into two or more well-structured tables to eliminate data duplication.
The goal is to construct tables such that each table has a single relation or theme |
|
|
Structured Query Language (SQL)
|
An international standard language for processing databases
Read data Insert data Modify data Delete data |
|
|
Relational Operations
|
1 Select: creates subsets of data of all records that meet stated criteria
2 Project: creates subsets of columns 3 Join: combines relational tables to provide users with more information that available in individual tables |
|
|
ACID rules
|
1 Atomicity: either all the tasks in a transaction must be done or none of them
2 Consistency: every transaction must preserve the integrity constraints 3 Isolation: two simultaneous transactions cannot interfere with one another 4 Durability: completed transactions cannot be aborted later or have their results discarded |
