LIS590IML Information Modeling * Class 07 Data Independence and
... ANSI/SPARC architecture, was aimed directly at the problems of data independence. • Informally: the relational model represents information as tables of values. • More formally: information is represented as a set of tuples, a relation. • “The model uses the mathematical concept of a relation…as its ...
... ANSI/SPARC architecture, was aimed directly at the problems of data independence. • Informally: the relational model represents information as tables of values. • More formally: information is represented as a set of tuples, a relation. • “The model uses the mathematical concept of a relation…as its ...
Distributed Databases PPT
... Using the Semijoin • To compute T1 join_cond T2 using a semijoin, first compute T1 join_cond T2 then join it with T2: attributes(T1)( T1 ...
... Using the Semijoin • To compute T1 join_cond T2 using a semijoin, first compute T1 join_cond T2 then join it with T2: attributes(T1)( T1 ...
1. Relational Model Concepts
... Ordering of attributes in a relation schema R (and of values within each tuple): o We will consider the attributes in R(A1, A2, ..., An) and the values in each t= to be ordered
o However, a more general definition of relation (which we will not use) does not
require attribute orderi ...
... Ordering of attributes in a relation schema R (and of values within each tuple): o We will consider the attributes in R(A1, A2, ..., An) and the values in each t=
XML Data Storage
... – Bottom-level elements and attributes are mapped to attributes of relations – A relation is created for each element type • An id attribute to store a unique id for each element • all element attributes become relation attributes • All subelements that occur only once become attributes – For text-v ...
... – Bottom-level elements and attributes are mapped to attributes of relations – A relation is created for each element type • An id attribute to store a unique id for each element • all element attributes become relation attributes • All subelements that occur only once become attributes – For text-v ...
Fundamental of Database Systems 1401312-3
... UNION (∪): The result of this operation, denoted by R∪S, is a relation that includes all tuples that are either in R or in S or in both R and S. Duplicate tuples are eliminated. INTERSECTION (∩): The result of this operation, denoted by R∩S, is a relation that includes all tuples that are in both Ra ...
... UNION (∪): The result of this operation, denoted by R∪S, is a relation that includes all tuples that are either in R or in S or in both R and S. Duplicate tuples are eliminated. INTERSECTION (∩): The result of this operation, denoted by R∩S, is a relation that includes all tuples that are in both Ra ...
The Relational Database Model
... Table: two-dimensional structure composed of rows and columns Persistent representation of logical relation Contains group of related entities = an entity set ...
... Table: two-dimensional structure composed of rows and columns Persistent representation of logical relation Contains group of related entities = an entity set ...
CS4416_-_Lec_01_Intr..
... The bar and beer together are the key for Sells: CREATE TABLE Sells ( bar CHAR(20), beer ...
... The bar and beer together are the key for Sells: CREATE TABLE Sells ( bar CHAR(20), beer ...
Q- Which of the following constraints enforces entity integrity?
... unique identifier for a row within a database table. allow any actions that would destroy links between tables ...
... unique identifier for a row within a database table. allow any actions that would destroy links between tables ...
Cost-based query optimization
... Based on data statistics and cost model for operators in physical relational algrebra ...
... Based on data statistics and cost model for operators in physical relational algrebra ...
PPT file
... vi is the value corresponding to attribute Ai. The components values of tuples are denoted as: •Both t[Ai] and t.Ai refer to the value vi in t for attribute Ai. •Both t[Au, Aw, …,Az] and t.(Au, Aw, …,Az), where Au, Aw, …,Az is a list of all attributes from R, refer to the subtuple of values < v1, v2 ...
... vi is the value corresponding to attribute Ai. The components values of tuples are denoted as: •Both t[Ai] and t.Ai refer to the value vi in t for attribute Ai. •Both t[Au, Aw, …,Az] and t.(Au, Aw, …,Az), where Au, Aw, …,Az is a list of all attributes from R, refer to the subtuple of values < v1, v2 ...
Overview of Databases I
... Requirements analysis: Find out what users want to do with the database Conceptual design: Use the output of RA to develop a high-level description of the data to be stored, along with their constraints. Output of CD usually is an ER-diagram. Logical design: Choose a DBMS and map the conceptual sche ...
... Requirements analysis: Find out what users want to do with the database Conceptual design: Use the output of RA to develop a high-level description of the data to be stored, along with their constraints. Output of CD usually is an ER-diagram. Logical design: Choose a DBMS and map the conceptual sche ...
RelationalCalculus
... type domains of the relational schema (domain calculus), or the set of all relations in the database (tuple calculus) can serve a model for it All meaningful sentences in the model are true or false, so the relation tuples can be interpreted as truthful facts describing the world The constraints des ...
... type domains of the relational schema (domain calculus), or the set of all relations in the database (tuple calculus) can serve a model for it All meaningful sentences in the model are true or false, so the relation tuples can be interpreted as truthful facts describing the world The constraints des ...
Chapter 9 Physical Database Design Methodology
... Disk I/O (os, database, index, recovery log) Network (traffic, collisions) File organization & access method ...
... Disk I/O (os, database, index, recovery log) Network (traffic, collisions) File organization & access method ...
reldb02
... Moreover, in the relational model, the term domain refers to the current set of values found under an attribute name. Thus, if the relation in Figure 2-4 is the only relation in the database, the domain of ‘Cname’ is the set {Codd, Martin, Deen}, while that of ‘Ccity’ is {London, Paris}. But if ther ...
... Moreover, in the relational model, the term domain refers to the current set of values found under an attribute name. Thus, if the relation in Figure 2-4 is the only relation in the database, the domain of ‘Cname’ is the set {Codd, Martin, Deen}, while that of ‘Ccity’ is {London, Paris}. But if ther ...
The Relational Model: Concepts - gozips.uakron.edu
... E.g. Query-by-Example (QBE), Relational Algebra, SQL and Relational Calculus Structured Query Language (SQL) – the language that defines and manipulates relational databases ...
... E.g. Query-by-Example (QBE), Relational Algebra, SQL and Relational Calculus Structured Query Language (SQL) – the language that defines and manipulates relational databases ...
CS206 --- Electronic Commerce
... Relation for a weak entity set must include attributes for its complete key (including those belonging to other entity sets), as well as its own, nonkey attributes. A supporting relationship is redundant and yields no relation (unless it has attributes). ...
... Relation for a weak entity set must include attributes for its complete key (including those belonging to other entity sets), as well as its own, nonkey attributes. A supporting relationship is redundant and yields no relation (unless it has attributes). ...