International relation

Classified in Computers

Written at on English with a size of 8.88 KB.

Database - organized collection of data, grouped into tables

Relational Database - tables are connected using relations and constraints. (Chief components: Entities and Relationships)

Relational data modeldescribing entities and their relationships

Selection -> filtering rows (tuples or records)

Projection -> filtering columns (attributes)

SQL is a standard language for querying and manipulating data

The number of tuples is the cardinality of the relation

The number of attributes is the arity of the relation

SQL Query :SELECT <attributes>  FROM <one or more relations> WHERE <conditions>

DISTINCT: Eliminating Duplicates - SELECT DISTINCT Category

Several equivalent ways to write a basic join in SQL:

SELECT PName, Price

FROM Product, Company

WHERE Manufacturer = CName

AND Country=‘Japan’

AND Price <= 200

SELECT PName, Price

FROM Product

JOIN Company ON Manufacturer = Cname

AND Country=‘Japan’

WHERE Price <= 200

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