We use this when we compare two colums from two different table .Based on equality or non equality, we retrieve the rows matched.
eg.
Select emp.empid , order.orderid
from emp Innerjoin order
on Emp.empid=order.empid
This example gives all the rows from emp,order tables where the empid's in both the tables are same.
Outer Join:
There are three types of outer joins namely:
Left Outer Join---For retreiving all the columns from the first table irrespective of the column match.
Right Outer Join---For retreiving all the columns from the second table irrespective of the column match
Full Outer Join---For retreiving all the columns from both the tables irrespective of column match.
Eg.
If we have two tables named stud1,stud2 with the following data
Stud1: id Name stud2: id Name
1 xxx 1 aaa
2 yyy 2 bbb
3 zzz 4 ccc
4 www 6 ddd
When we use Left Outer Join we get the output as:
1 aaa
2 bbb
3
4 ccc
When we use Right Outer Join we get the output as:
1 aaa
2 bbb
4 ccc
When we use Full Outer Join we get the output as:
1 aaa
2 bbb
3
4 ccc
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