Data Flashcards
What are 4 of the most common database models?
- Flat-file
- Relational
- Hierarchical
- Object-oriented
What are the two major layers of a database application?
- Application layer
- Database management layer
What is a flat-file database?
Info stored?
Info separated
Limitation
Stores data in a plain text file.
Each line of the text holds one record.
Fields are separated by delimiters like spaces or comas.
Cannot contain multiple tables
What kinds of operations can be performed on a flat-file database? (4)
- Creating
- Deleting
- Updating
- Searching
What is a hierarchical Database?
One of the oldest database models organized in a tree structure like an organizational chart.
What is a relational database?
Contain tables that can be joined together in logical ways.
What does SQL do?
Includes queries to identify what data should be retrieved or how the data should be manipulated.
What does the selection operation do?
Takes rows from one table and creates a new table.
User specifies the table the rows are taken from and tests selection criterion. Selection is tested against each row and when a condition is met, that row is included in result table.
Select does what in SQL?
Identifies records being requested
(*) means what in SQL
Everything form the selected table
From in SQL
Identifies the table name
Where does what in SQL
Identifies the condition the query is requesting
What is Union Operation?
Combines distinct fields from multiple tables that have the same set of attributes and data types.
What is product operation?
Creates a result table that includes all the attributes from the two tables.
Each row of the second table is added to each row of the first table.
What is a join operation/What does it do?
Combines two tables but records are only appended when a matching criterion is met.
Resulting table includes a row with the attributes of both tables only when attributes from the first database table match related attributes from the second database table
What is an object oriented database?
What are the two components of OO
Stores complex data and relationships between data directly without using inner-table relations.
A collection of objects, each with two components
1. the data and
2. instructions (or software programs called methods)
Key-Value databases do what?
Store each item as an attribute name (key) together with its value
Graph stores do what?
Store information about networks of data such as social connections
Wide-column stores do what
Optimized for queries on large data sets and store columns of data together instead of rows.
Document-format databases do what?
Pairs each key with a complex data structure known as a document. Documents can contain many different key-value pairs