Mid Term Flashcards
What does DML stand for?
Data Manipulation Language
What is the purpose of DML operations?
To manipulate the table.
3 types of DML operations?
- Insert
- delete
- Update
A notation for describing data or information
A data model
What are 3 ways a data model can describe data?
- Structure of the data
- Operations on the data
- Constraints on the data
Represents data in 2-D table (rows and columns)
Relations
True me false: Table, entity, and relation are the same?
True
The columns of a relation are called?
Attributes
What do attributes describe?
The meaning of entries in the column
What is a logical structure for data?
Schema
The set of schemas for the relations in a relational database are called?
Relational Database Schema
The name of a relation and the set of attributes for a relation?
Schema (for relation)
What is ‘a set’?
The attributes in a relation schema
True or False: Rows and Tuples are the same thing?
True
What are tuples?
The rows of a relation, minus the header.
What is the relationship between an attribute and a domain?
Each attribute of a relation is a domain
What are the two parts of a relation?
- Schema
- Instance
Formal term for ‘Table’
Relation
Formal term for ‘Column’
Attribute
Formal term for ‘Row’
Tuple
Formal term for values in a Column
Domain
Formal term for Table Definition
Relation Schema
Formal term for populated Table
Relation Instance/Extension
Properties of relations
- No duplicate tuples
- Tuples have no order
- No duplicate attributes
- Attributes have no order
- Every tuple must have attribute values from each of the domains or NULL
T/F: Tuples are unordered
True
T/F: Attributes are unordered
True
What are two ways to declare a key in the CREATETABLE statement?
- Declare 1 attribute when listed in the relation schema
- Add an additional declaration identifying a listed attribute or set of attributes which form the key
A specific type of field in a relational database that can identify each unique record independently of any other data.
Candidate Key
A column or group of columns in a relational database table that provides a link between data in two relations.
Foreign Key
A special relational database table column (or combination of columns) designated to uniquely identify each table record.
Primary Key
a candidate key that consists of two or more attributes that together uniquely identify an entity occurrence
Composite Key
What is a stored relation?
Table
Relations defined by computation. They are not stored but are constructed when needed.
Views
Relations created by SQL language processor when executing queries and data modifications.
Temporary Tables
Data objects that either identify or describe entities…
Attributes
What are two types of attributes?
- Simple Attribute
- Composite Attribute
An attribute that cannot be sub-divided
Simple Attribute
An attribute that can be sub-divided to yield additional attributes
Composite Attribute
An attribute that is not physically stored within the database; derived by algorithm
Derived Attribute
An attribute that can only have a single atomic value
Single-valued Attribute
An attribute that can have many values
Multi-valued Attribute
Connections among two or more entity sets are called…
Relations
The maximum number of times an instance in one entity can be associated with instances in a related entity
Cardinality
The minimum number of times an instance in one entity can be associated with an instance in a related entity
Modality
Cardinality values
One or Many
Modality Values
One or Zero
In ER Diagrams entity sets are represented by…
Rectangles
In ER Diagrams attributes are represented by…
Ovals
In ER Diagrams relationships are represented by…
Diamonds
Requires that if a value of one attribute of a relation references a value of another attribute, then the referenced value must exist.
Referential Integrity Constraint
A collection of data that is managed by a DBMS…
Database
A software tool for managing data in a database
Database Management System (DBMS)
If a DMBS is for a relational database?
RDMBS
How does DMBS allow users to define schema (structure)?
Data Definition Language (DDL)
How does DMBS allow users to query (question) or modify the data?
Data Manipulation Language (DML)
What are the two types of languages used by DMBS?
- Data Definition Language (DDL)
- Data Manipulation Language (DML)
In SQL, what is projection?
When you add criteria
