Inner join
outer join--left outer join ,right outer join , full outer 
join
Cross Join

Inner join: This type of join displays matched rows from 
tables.
this is based on equality condition ,so also called 
equijoin.
exp- select empid,d.deptid,deptname,empname,location,salary
from emp e inner join dept d on e.deptid=d.deptid

Cross join: this is not based on any condition. It results 
every  row of one table matching with every row of another 
table.
exp- select * from emp cross join dept

Self join: This ype of join joins a table to itself.
 

outer join:
Three types -
a.left outer join: It reults mathed rows from both tables 
as well as all unmatched rows from left table.
exp- select empid,d.deptid,deptname,name,location,salary
from emp e left outer join dept d
on e.emp=d.dept

 it displays all data from emp table .

right Outer join:It reults mathed rows from both tables as 
well as all unmatched rows from right table.
exp- select empid,d.deptid,deptname,name,location,salary
from emp e right outer join dept d
on e.emp=d.dept

 it displays all data from dept table .

 Full Outer Join: This type of join results all matched 
rows from both tables as well as umatched rows from both 
tables.
exp.-select empid,d.deptid,deptname,name,location,salary
from emp e full outer join dept d
 on emp e=d.dept d
 It displays all matched and unmatched rows from both emp  
and dept tables.