Department of Computer Science
Basic Properties of a Table
3. The order of the columns is
immaterial
4. The order of the rows is
immaterial
5. Each row/tuple/record is
distinct, no two rows can be
same
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Fundamentals of Database Management: Table Properties, Mathematical Relations, and Keys, Slides of Distributed Database Management Systems
An introduction to the basic concepts of database management, focusing on the properties of tables, mathematical relations, and keys. It covers the immaterial order of columns and rows in a table, the concept of cartesian products and relations, and the importance of superkeys, candidate keys, primary keys, and foreign keys in maintaining data integrity.
Typology: Slides
2011/2012
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Basic Properties of a Table
3. The order of the columns is
immaterial
4. The order of the rows is
immaterial
5. Each row/tuple/record is
distinct, no two rows can be
same
A table
stID stName clName doB gen der S001 M. Suhail MCS 12/6/84 M
S002 M. Shahid BCS 3/9/86 M
S003 Naila S. MCS 7/8/85 F
S004 Rubab A. MBA 23/4/86 F
S005 Ehsan M. BBA 22/7/88 M
Mathematical Relations
Consider two sets
A = {x, y} B = {2, 4, 6}
Cartesian product of these sets
A X B= {(x,2), (x,4), (x,6), (y,2), (y,4),
(y,6)}
Mathematical Relations
A relation is some subset of this
Cartesian product, For example,
R1= {(x,2), (y,2),(x,6),(x,4)}
R2 = {(x,4), (y,6), (y,4)}
Database Relations
Thinking in some real world
scenario
Name = {Ali, Sana, Ahmed, Sara}
Age = {15,16,17,18,…….,25}
Database Relations
Cartesian product of Name & Age
Name X Age= {(Ali,15), (Sana,15), (Ahmed,15), (Sara,15), …., (Ahmed,25), (Sara,25)}
CLASS = {(Ali, 18), (Sana, 17), (Ali, 20), (Ahmed, 19)}
Relation Scheme
Can be represented as
R = (A1:D1, A2:D2, ……, An:Dn)
STD = (stId:Text, stName: text,
stAdres:Text, doB:Date) OR
STD(stId, stName, stAdres, doB)
Database Relations
According to this scheme we can have
a relation (instance of this scheme),
like
STD={(stId:S001, stName:Ali, stAdres:
Lahore, doB:12/12/76), (stId:S003, stName:A. Rehman, stAdres: RWP, doB:2/12/77)}
DB and Math Relations
Properties of DB relations are
similar to those of Mathematical
relations, except
The order of columns in
Mathematical relation does matter
Degree and Cardinality
The number of rows in a
relation is its cardinality and
the number of columns is its
degree
Relational Keys
Primary Key
- Candidate key selected to identify tuples uniquely within relation.
Alternate Keys
- Candidate keys that are not selected to be primary key.
Foreign Key
- Attribute, or set of attributes, within one relation that matches candidate key of some (possibly same) relation.
Relations Keys
Foreign Key: An attribute of a
table B that is primary key in
another table A
Consider table EMP and DEPT
EMP ( empId , empName, qual, depId)
DEPT ( depId , depName, numEmp)
Significance of Constraints
Constraints help to maintain the
correctness, validity or integrity
of the database
Like null constrains, default
value, domain constraint
48
Views
Base Relation
- Named relation corresponding to an entity in conceptual schema, whose tuples are physically stored in database.
View
- Dynamic result of one or more relational operations operating on base relations to produce another relation.