Distributed Database Management Systems: Lecture 7. The main topics covered in this chapter include: relational data languages; relational calculus based, non-procedural, user only mentions the relationships among the data; cartesian product;...
Trang 1Distributed Database Management System
Lecture 7
Trang 2Relational Data Languages
procedural, user is to specify in terms of certain operations, how result is to be obtained
non-procedural, user only mentions the relationships among the data
Trang 3• Relational Algebra based,
Procedural
Non-Procedural
Five basic operations
– Selection, Projection, Union, Set
difference and Cartesian Product
Trang 4• Five others
– Intersection, -join, natural join, semi-join and quotient – Unary and Binary ops
– Union Compatibility
predicate calculus
Trang 5• Symbol alphabet
1.Var, constraints, functions, predicate symbols
2.Parentheses
3.Logical connectors
4.Quantifiers
Trang 6Example
Trang 7relation
Trang 8relation
Trang 9Set Difference
are not in S
Trang 10Cartesian Product
concatenated with each of other
Trang 11relations
Trang 12Theta Join
from both tables
Trang 13Natural Join