Logical Data Modellin

Question

Dear All
Could you explain about Logical Datamodeling using Explain Plan and TKProf.
When we will for Outerjoin in real time applications..
Thanks and Regards
B.Rangarajan[b]

Answer 1

not sure what you are asking in the fast part.
but here is an example for outer join.
drop table master
create table master
(id number primary key
,name varchar2(256))
insert into master values(1, 'Accounts')
insert into master values(2, 'Sales')
drop table detail
create table detail
(id number primary key
,ename varchar2(256)
,masterid number references master)
insert into detail values(1,'Scott',1)
now when you perform an equi join on the two tables
to get the employee and the department name in which
he is working, you get only one record with the below query.
set linesize 100
column dname format a32
column ename format a32
select name dname , ename
from master,detail
where master.id=detail.masterid
You will not get the sales record from the mater table becuase there
are no corresponding records for this in the child table.
But when you also want to display the departments which does not
have employees then the outer join comes into picture.
set linesize 100
column dname format a32
column ename format a32
select name dname , ename
from master,detail
where master.id=detail.masterid(+)
Now you should get sales records also in the results.
the plus is added towards the detail table becuase the
records are missing in that table.