Note remember page numbers
Student Subjects Sid Name Class Subject. Alex 10 Math Maria 10 English music 11 Sports Equijoin
Student Student. class = subjects. class Subjects
Sid Name class Subject 101 Alex 10 10 Math Alex Maria 10 0 English=music 102 Maria Sports
Ana- Hierarchical
"In this model to Store data
Relational
Network
It organizes records in the form of table and relationship between tables are set using Common fields.
It organizes records to one another through links or pointers.
hierarchy method is used. It is the oldest method and not in use today.
2) To organize records, it uses tree Structure.
It organizes records in the form of directed graphs.
It organizes records in the form of tables.
provides data independence
3) This model lacks. data independence.
There is partial date independence
key A unique, indexed field is used to search for a data element.
is very difficult since One can retrieve a child
4) Searching for a record
only after going
through its parent
Searching for record is easy since there are multiple access faths to adata
element.
record.
Road ID 12 34 Distance Road Name 22 Hamilton 1384 34
Windstam 39 Wind stam 14 16 Select Road ID From Road
Where distance = 22 or distance = 33,
(Query 2 ->
Select distinct Road Name
from Road;
Query 3 →
Select distinct Road Name
From Road Order by Road Name; Query 4 Select From Road.Where Toad ID = 12 34 and Distance = 22,
Name Specialization doctor treatment, addres Patient Name Disease Phone No Disease Examination Work for Test Hospital Ant User External view External View Conceptual Schema Internal Schema Database
External view level-> Several users can view their desired data from this level.
Conceptual level-> relationship among data, schema of data etc. are described in this level.
(3) Interna devel-> This level describes how the data is. actually stored in the storage devices.
create table r(a int,b int,c int,d int);insert into r values (1,2,3,4);insert into r values (2,2,6,1);insert into r values (3,2,2,6);insert into r values (4,2,4,2);
Another table
create table s(c int,d int,e int,f int);
insert into s values (4,2,4,2);
insert into s values (3,4,6,4);
insert into s values (2,2,6,1);
insert into s values (4,2,5,3);
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